NAIC Newsletter Number 32

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STRONOMY AND IONOSPHE

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ARECIBO OBSERVATORY

Photo: David Parker, 1997/Science Photo Library

The NAIC is operated by Cornell University under a Cooperative Agreement with the National Science Foundation.

March 2001, Number 32

INDEX

Resetting the Primary Reflector ..... 1

Radio Astronomy Highlights ........... 4

Observing with the Upgraded Arecibo

Telescope ....................................... 5

Space and Atmospheric Sciences .. 12

Planetary Science ........................... 16

Computer Department News ........ 16

Employee of the Year 2000 ............ 17

A School Science Project ................ 17

Visit from Congressional Staffers . 19

Colloquia since the last Newsletter 19

Comings and Goings ...................... 19

Observing Proposal Reminder: The next proposal deadline is June 1, 2001. Please make a note to get your proposalsfor observations using the Arecibo Observatory facilities submitted by that date. Details can be found at our web sitehttp://www.naic.edu/vscience/proposal/proposal.htm.

Resetting the Arecibo PrimaryReflector Surface

Paul Goldsmith

Although not strictly considered partof the Arecibo Upgrade project, the

surface of the 305 m telescope plays acritical role in the overall system per-formance, particularly at the higher fre-

Figure 1: An image of the errors in the main reflector surface processed from Lynn Baker’s photogram-metry data by Germán Cortés. Blue indicates positive devation from an ideal surface and red/yellow

means negative deviation. The unweighted rms is about 15 mm. (Courtesy Germán Cortés).

NAIC/AO NewsletterMarch 2001, Number 32 2

quencies that is one goal of the Upgrade.The surface was last surveyed and ad-justed about 15 years ago, and a lot hashappened since. The main cables sup-porting the surface are held to the groundby about 2000 cables which connect toconcrete blocks sitting on the ground be-neath the reflector. Soil motions thus candirectly impact the shape of the reflec-tor surface.

Based on monitoring by surveying,José Maldonado (NAIC) had indicationsthat these motions had been significant,particularly in the southeast quadrant ofthe reflector. That part of the natural“sinkhole” in which the reflector wasbuilt had been filled in extensively withdirt and construction material from oth-er parts of the bowl and elsewhere. Thisarea was less stable than the rest of theground, and it was not surprising that itshould be more subject to gradual move-ment. Puerto Rico is in a fairly activeseismic zone and there are tremors thatproduce small motions—in particular, ofthis not very well compacted portion ofthe ground under the reflector.

In addition to the subsidence, theupgrade work itself was quite traumaticfor the reflector surface. There weremany panels damaged by items droppedby construction crew working on theplatform and the feed arm. Also, therewas one large cable that was dropped,and when this hit the dish surface, it de-stroyed over 100 panels, and broke someof the cables that support the dish sur-face. These panels and cables have longbeen repaired, but the process may cer-tainly have contributed to a deteriorationof the accuracy of the reflector surface.

Since one of the major goals of theupgrade was to raise the upper frequen-cy limit of operation to 8 GHz or higher(wavelengths less than 4 cm and hope-fully as short as 3 cm) it was evident thatwe would be pushing the accuracy of theprimary reflector. Some very limitedtests using the mini-Gregorian carriedout by Phil Perillat (NAIC) in April 1991showed that things were not terrific inthis frequency range, with a sensitivity

of 0.25 K/Jy at 10.67 GHz. And this wasbefore the contractors started redoing thesurface for us! The mini-Gregorian il-luminated only a small fraction of thetotal surface, but the derived surface rmsfrom those measurements was 3.3 mm—not too terrible, but higher than onewould like for efficient operation.

Previous campaigns to set the prima-ry reflector were based on optical sur-veys with theodolites. In this procedure,the location of targets located above themain (North-South) cables was deter-mined by triangulation based on mea-surements made from several pointsaround the reflector rim. The locationsof these selected points could be mea-sured and adjusted to an accuracy of ap-proximately 1 mm rms. However, thepanels are only 1/4 the size of the spac-ing of the main cables, and each of themcan be adjusted. In the approach usedearlier, the positions of panels betweenthe main cables were “interpolated” be-tween the measurements of the widely-spaced targets on the main cables. It wasthought that the overall rms was on theorder of 2.5 mm, only slightly less thanimplied by the X-band measurementsmentioned above.

To perform really well, one needs theoverall rms surface error to be less than1/20 wavelength, which translates to 3mm rms at 10 GHz. The panels them-selves are thought to have an error ofapproximately 1 mm rms, and the sec-ondary and tertiary reflectors contributesmaller errors. So it would be desirableto get the primary surface adjustmenterror below 2 mm rms. It was judgedimpractical to reach this level using thetechnique employed previously. In as-sessing options, we decided to adoptoptical photogrammetry.

For this approach, reflective targetsare put on the panels; these targets are 3inch diameter disks of retroreflectivematerial. Using a special camera, pho-tographs of the dish are taken from thetop of each of the towers. You can imag-ine each photograph as yielding the an-gular coordinates of the target. If you

combine the angles to a given target fromthree or more viewing positions, you cansolve for the three dimensional locationof the target. This technique has beenrefined and turned into a commerciallyavailable combination of hardware andsoftware by a company called GeodeticServices Inc. NAIC has been workingwith the president of GSI, Mr. JohnBrown, since 1994, and last year we fi-nally were able to get an order in for thespecial equipment needed. A somewhatdifferent version of this same approachwas used to measure the secondary andtertiary reflectors—the main differenceis for those relatively small reflectors, aCCD camera was used.

For the measurement of the primary,we have to use a large-format film cam-era. Part of the reason why is evident ifyou compare the number of pixels in a 6inch by 8 inch piece of film, versus eventhe biggest “megapixel” CCD. My crudeestimate is that we get at least a “gigapix-el” format with the film camera. This isnecessary if you want to measure a tar-get 500 m away to an accuracy of 1 mm.

What happens in practice is that thecamera is taken up to the top of one ofthe towers. It is accompanied by severalintrepid NAIC staff members, typicallyLynn Baker, Felipe Soberal, and some-times others. From the tower top, theytake a number of photographs of the dishsurface—several photographs are neces-sary to cover the entire area, and theyalso take photographs with the camerarotated by 90 degrees to be able to iso-late any distortion in the camera’s imag-ing system, and take views from twodifferent positions on each tower top aswell. The illumination is provided by apowerful strobe lamp, which togetherwith the retroreflective properties of thetarget, guarantees that the targets standout with good contrast relative to thegeneral dish surface. It also means thatthe effective exposure time is very short,minimizing any mechanical vibrations,etc. Getting all the required equipmentto the tower tops is no mean feat, and wehave to admire those who carried out thisdifficult and sometimes hazardous work.


After the photographs are taken, thefilm is developed, and then each imageis digitized using a special scanner thatis located in lab adjacent to Tony Ace-vedo’s (NAIC) office. This scanner is aclose relative to plate measuring ma-chines used by astronomers; it measuresthe centroid of each of the “spots” pro-duced by the targets to an error of nomore than a few microns. These cen-troid positions are entered into a data fileon the PC controlling the scanner.

After all the photographs arescanned, the data files are combined us-ing a special program developed by GSI,which outputs the location of each tar-get in three coordinates. Next, Lynn fitsa sphere to the data set, and derives theerrors for each target relative to the best-fit sphere. The software also gives theuncertainty in each position; this dependson where on the dish the target is locat-ed, and in how many photographs thetarget appears. We have been impressedthat the formal uncertainty in positionwhen we have a full set of photographsis about 0.6 mm rms. Thus, the systemappears to really have the capability tomeasure the whole surface to the re-quired accuracy, but then it will be up tous to adjust the panels to achieve ourgoal.

During the Fall of 2000, about 2,000targets were placed on the primary sur-face of the antenna. Most of these werelocated above the points where the “tie-back cables” (which connect the surfaceto the concrete anchors on the groundbelow, mentioned above) are located.Some extra targets were put in densepatches to fully sample the panel-to-pan-el setting errors. It was a real struggle toget the necessary data, as that was oneof the rainiest Fall periods in recentmemory, but this was finally accom-plished. The usual learning curve for de-veloping, scanning, and reducing datawas ascended, and we obtained the firstset of post-upgrade surface measurementdata.

An image of the errors (processedfrom Lynn Baker’s data by Germán

Cortés—NAIC) is shown in Figure 1.Blue means high and red/yellow meanslow. The big surprise is that the un-weighted rms is about 15 mm! This isworse than had been determined in 1991.The obvious conclusion is that all theupgrade work (plus the passage of theintervening 10 years!) severely degrad-ed the surface accuracy. It is difficult tocompare this photogrammetric rms di-rectly with that derived radiometrically,because the Gregorian system does notilluminate the entire surface, and largescale errors of the illuminated region(linear gradients and quadratic errors) aretaken out by calibration runs, appearingas pointing and focus offsets, respective-ly. However, there is no doubt that wehave adequate explanation for the rela-tively poor performance we have seenat 5 GHz, and also for the variability ofgain as a function of source declinationand hour angle. Note in particular thelarge errors seen in the “fill area”. Thelarge errors seen in the panels right atthe center of the dish are not surprisingas those are the “new” panels recently

installed by José Maldonado’s team, andthey have not yet been adjusted. Thelargest errors outside the center are onthe order of 100 mm! This is even big-ger than José Maldonado had expected,and shows how much that part of the dishsurface had sunk.

While the first round of photogram-metry was going on, José Maldonadoand his crew were undertaking to refur-bish a lot of the panel support hardwarethat had corroded since installation in1974. Several thousand panel supportsneeded to be replaced, and many moreto be cleaned up and greased so that ad-justment of the individual panels wouldbe possible. This work is still ongoing,and should be completed in April 2001.

That work was interrupted by the ar-rival of the results of the first round ofphotogrammetry indicating the presenceof very severe large-scale errors. Weimmediately started a project to adjustthe 2000 or so tieback cables to get thesurface closer to the desired sphericalshape. This work was completed in a

Figure 2: This image is from the second set of photogrammetry tests completed in January by Lynn

Baker and Felipe Soberal. The improvement is immediately evident when compared with Figure 1,and is quantified by the reduction in the rms surface error from ~15 mm to just over 5 mm.


remarkably short time, and in JanuaryLynn went again to Arecibo, and withFelipe obtained a second set of data,which is shown in Figure 2. The im-provement is immediately evident (thecolor tables are the same), and is quanti-fied by the reduction in the rms surfaceerror from ~15 mm to just over 5 mm.The situation is really somewhat better.If one allows for fact that some of theadjustments were done in the wrong di-rection (something that always happensin a campaign like this, despite the bestefforts of the field crews), and one ex-cludes them, the rms is down to about3.5 mm. Again, this does not allow forany low-order terms, and includes theentire antenna surface (except the cen-tral panels which still were not adjust-ed). Part of the remaining error may bedue to the fact that some of the adjust-ments were so large that there were in-teractions between adjustment points andpossibly even nonlinearities in the rela-tionship between tieback cables and sur-face position.

Naturally, although this already rep-resents a huge improvement, we are notsatisfied, and a second set of requiredadjustments has been generated. As thisis written, over half of the tieback cableturnbuckles have already been adjustedfor the second time. The central panelswill also be included in this round. Sowe can really hope to get the large-scalerms down to a few mm. Unfortunately,this has all happened so quickly that wehave not had time to schedule the re-quired telescope time to see what hashappened to the antenna performance. Insome limited time creatively obtained byJohn Harmon (and thanks to those whogave up their scheduled observations!)Phil Perillat and Mike Nolan (NAIC) didcarry out some measurements. There areindications (but these must be consideredpreliminary) that the L-band gain maybe up by about 10%, that the S-band gainis up from 5.5 to 7.0 K/Jy, and that at C-band (5 GHz) we have a single beamwith 4 - 5 K/Jy consistently. I am goingout on a limb to even put these results inprint, but I know that they are what ev-eryone wants to hear about. I caution

again that these are very preliminary.However, I am confident that the photo-grammetry is giving us the right answers,and that we can do better yet.

So —what happens next? After wecomplete the ongoing second round oftieback cable adjustments, Lynn andFelipe will do the photogrammetry for athird time. We also will be schedulingadditional telescope time to define theantenna performance more completely.This is all a prelude for Phase II, in whichwe adjust the position of each panel in-dividually. The first step here is to getapproximately 39,000 targets out on theantenna surface. The targets themselvesare currently on order and should arrivewithin a month or so. By that time, allof the panel support hardware should berefurbished, and the nontrivial task ofputting those targets on the antenna sur-face will be accomplished. Then, thereally demanding job of doing the pho-togrammetry, but measuring 39,000 rath-er than 2,000 targets will begin. This isconceptually not different, but in prac-tice the amount of time and effort to scanthe photographs will increase greatly,simply due to the increased number oftargets.

Adjustment of the individual panelscan then begin, and this too may requireseveral iterations. Thus, this project islikely to go on for another year. In addi-tion to the surface adjustment itself, wewill be installing the tertiary actuatorsand computer control system, which willbe necessary to make the small focus andpointing corrections necessary for oper-ation at the shortest wavelengths. BillSisk (NAIC) has been working with thissystem extensively and it is almost readyto go, but installation needs to be syn-chronized with a couple of other nastytasks including shimming the elevationrails. It does seem that efficient opera-tion at 5 GHz is now within our grasp,and 10 GHz is not too far off. I hopethat in the next newsletter we can giveyou some detailed results of antennameasurements at the higher frequencies,and before long, some scientific resultsas well.

Radio Astronomy Highlights

Chris Salter

Pulsar Scintillations

The Oberlin/Cornell collaborationlead by Dan Stinebring (Oberlin)

continues to investigate the high-Q “par-abolic arcs” that they have been seen inpulsar secondary spectra (power spectraof the dynamic spectra). These arcs,which are the transform domain equiva-lent of the criss-cross patterns that haveoften been noted in pulsar dynamic spec-tra since the early 1970s, will be famil-iar to faithful readers of these pages. Infact, these arcs made their debut as“wisps” in the Spring 1999 NAIC-AONewsletter (No. 27) after the group madeintensive observations during January,1999. It will interest some readers thatthat article caught the attention of noneother than Ronald Bracewell, who hadsome interesting suggestions to makeconcerning further analysis of the pat-terns.

In addition to roughly biweekly ob-servations — mostly performed remote-ly — that the group makes to monitortime variability of the phenomenon to-ward half a dozen strong, nearby pulsars,they are continuing to explore the effectin archival data, much of it taken atArecibo by Jim Cordes (Cornell) duringthe 1980s. The most remarkable resultto come out of the analysis of this earlierdata is how little the arc pattern changes

As indicated above, many peoplehave been working very hard on the sur-face adjustment project. Lynn Baker,Don Campbell (NAIC), José Maldona-do, Mike Nolan, Phil Perillat, and FelipeSoberal have been extensively involved,and they have been supported by manyothers at Arecibo and also in the NAICMaple Avenue laboratory. Mr. JohnBrown of GSI has been extremely help-ful in getting us up to speed with the pho-togrammetry system at Arecibo. Thesepeople are the ones who deserve creditfor getting Arecibo working through theentire cm wavelength range.


for a particular pulsar over more thantwenty years! The basic curvature of thearc, which they believe is fixed by thelocation of a dominant scattering screenalong the line of sight, as well as the tilt(with respect to the pulsar velocity vec-tor) of “filamentary” structure in theplane of the screen, stays roughly con-stant over two decades. Work continueson making this statement quantitative, aswell as inferring an axial ratio for thesecondary image that they believe is re-sponsible for the parabolic arc when itinterferes with direct rays from the main(compact) pulsar image. Further detailsof this work can be found in Stinebringet al. (ApJ, 549, L97).

Pulsar Timing

As part of a program to time some pul-sars from the Parkes Multibeam surveythat lie in the Arecibo sky, Ingrid Stairs(NRAO), Fernando Camilo (Columbia),and other members of the multibeamsurvey collaboration have been makingregular Arecibo observations of the 71-ms binary pulsar J1904+0412 using thePSPM. The orbital parameters of this14.9-day circular-orbit binary systemimply that the mass of the companionstar is at least 0.2 M�. The pulsar is amember of the growing number of so-called intermediate-mass binary pulsar

(IMBP) systems, where the companionstar is thought to be a CO white dwarf.IMBPs differ from the classical millisec-ond pulsar low-mass white dwarf sys-tems in that the radio pulsars in IMBPshave longer spin periods and higher in-ferred surface magnetic field strengths,as well as significantly larger (but stillessentially circular) orbital eccentricities.Despite the necessarily poor statistics atthis stage, there are also suggestions thatthe scale height of IMBPs above andbelow the Galactic plane is a factor of 2-4 times smaller than for the millisecondpulsars. These various different proper-ties point to a different origin for theIMBPs, distinct from either the low orhigh-mass X-ray binary systems whichare thought to produce millisecond pul-sars and double neutron star binary sys-tems respectively. To date, the Parkessurvey has found 5 such systems, andfull details are given in Camilo et al.,(ApJ, 548, L187).

Pulsar Signal Processing

Motivated primarily by the need to ana-lyze fast-sampled data that is now pour-ing out of the Wide-band Arecibo PulsarProcessor (WAPP), Dunc Lorimer(NAIC) has just finished the initial re-lease of the SIGPROC pulsar signal pro-cessing package, (suggestions for a morecatchy acronym are most welcome!).

SIGPROC converts raw fast-sampleddata into a standard filter-bank formatfor subsequent processing. Folding anddedispersion of the filter-bank data isalso incorporated into the SIGPROCpackage, the idea being that the generaluser can produce data products quicklyfor use with other software packages.Applications of SIGPROC to date in-clude searches, polarimetry, scintillationand single-pulse studies (see Fig. 3 foran example of single pulses from the mil-lisecond pulsar, J1713+0747). In addi-tion to WAPP data, SIGPROC can readin data from the Penn State Pulsar Ma-chine (PSPM), and the filter-bank at theOoty Radio Telescope (ORT). Work con-tinues on extending the range of pulsarmachines catered for to include theAOFTM and the Berkeley Pulsar Pro-cessors. SIGPROC has been extensive-ly tested and documented and is availablefor download from the Arecibo Pulsarpage, (http://www.naic.edu/~pulsar).

Polarimetry Software

In parallel with the SIGPROC develop-ment effort, Jim Cordes has been adapt-ing existing software from the old NAIC/Berkeley 40-MHz correlator to reducepolarimetry data taken with the WAPP.The package takes folded correlationfunctions from SIGPROC as input to

Observing with the Upgraded Arecibo Telescope: Methods and Recent Results

AAS Special Session, Thursday, 05 June 2001 Pasadena, CA

Arecibo Observatory will be having a special session at the upcoming American Astronomical Society meeting inPasadena, entitled “Observing with the Upgraded Arecibo Telescope: Methods and Recent Results”. This is motivatedby the significant number of improvements to the Arecibo telescope which have been made within last seven years—including improvements in telescope sensitivity, correlator response, observing methods, and data reduction techniques.The purpose of this session will be to familiarize the community with these changes and to demonstrate the observingpossibilities with the upgraded telescope. It will start with a general introduction to the capabilities of the Arecibosystem, including telescope sensitivity and performance, available receivers, observing procedures (both for on-siteand remote observing), and data reduction options. This will be followed by a variety of shorter talks chosen todemonstrate the variety of observing possibilities at Arecibo, from Zeeman studies through asteroid imaging. Therewill also be a contributed poster session to complement this special session.

If you are interested in giving a talk or poster at this session, please send a preliminary title to [email protected] by7 March, 2001. For questions, please contact Karen O’Neil ([email protected]).


produce fully calibrated Stokes profiles.Flux calibration uses a pulsed noise di-ode calibrated against extragalacticsources of known flux densities. Thesoftware can correct for cross couplingin the feed system, and it can derotatethe polarization ellipse versus frequen-cy to account for Faraday rotation acrossthe band and for the differential timedelay between the two polarization chan-nels. Alternatively, the polarization an-gle rotation can be fitted to determinethe Faraday Rotation Measure. The soft-ware will be released for general useshortly, pending the finalizing of a num-ber of scripts to streamline the data re-duction process. A sample output profilefrom the package is shown in Fig. 4.

Pulsar Absorption Study of VerySmall Scale Structure in the ISM

For many years there has been theoreti-cal and observational support for struc-ture in the ISM on scales from ~1 pc to1 kpc (Dickey & Lockman, 1990,ARA&A, 28, 215), while structures onscales smaller than 1 pc were expectedto make only a tiny contribution. How-ever, more recent observations have re-vealed structure in the atomic, molecularand ionized gas that is orders of magni-tude smaller (5 –100 AU) and higher indensity (~104–5 cm-3) than previouslysuspected. This tiny-scale structure hasbeen found in all directions in which ithas been searched for and in all of thedifferent phases of the ISM, suggestingthat it is more likely to be a general prop-erty of the ISM than the effect of somelocal phenomenon. However, its originand existence still remain a puzzle. Fur-thermore, its presence poses seriousquestions for the models of the ISM, asthe over-density of these features sug-gests they are not in pressure equilibri-um with other components of the ISM.

One of the principal techniques forstudying very small scale features in thecold atomic medium is based on multi-epoch HI absorption measurements to-wards pulsars. As pulsars move quicklythrough the ISM, our line-of-sight at dif-ferent epochs samples different interven-

Figure 3: Signal-to-noise ratios of single pulses from the 4.57-ms pulsar J1713+0747 observed at L-bandusing the WAPP. Inset: a 100-ms time series showing the single pulses. The signal-to-noise distribution of the

pulses is very similar to those of long-period pulsars which indicates that the emission process is the same in

millisecond pulsars. (Courtesy Dunc Lorimer)

Single pulses from PSR J1713+0747

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B1929+10 MJD 51853.863 1.4750 GHz 100 MHz

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Figure 4: Polarization profiles for PSR B1929+10 observed with the WAPP. The top panel shows the total

intensity, linearly polarized flux density, and circular polarization (negative-going curve). The integrationtime was about 20 s and the circular polarization has not been corrected for cross coupling. The software

package allows correction if the relevant parameters are known. The non-randomness of the position angle

(lower panel) is real, owing to the close alignment of the spin and magnetic axes in this pulsar. (Courtesy JimCordes)


ing clouds. Comparison of spectra tak-en at different epochs gives informationabout the size of intervening clouds, theirdensity and pressure, as well as the frac-tion of the cold ISM gas they comprise.

Joel Weisberg (Carleton), SnezanaStanimirovic (NAIC), Stuart Anderson,Rick Jenet (Caltech), Simon Johnston(Sydney), Kiriaki Xilouris (UVA), andCarleton undergraduate students, AbbyHedden, Katie Devine, Amanda Kir-schner, & Kenji Spielman have under-taken multi-epoch HI-absorptionArecibo observations towards six brightpulsars. The main aim of this project isto probe smaller ISM clouds with high-er velocity resolution than has beenachieved by previous studies (e.g. Frail,Weisberg, Cordes & Mathers, 1994, ApJ,436, 144). The data are recorded withthe Caltech Baseband Recorder (CBR),and data processing is done remotelyusing a supercomputer and a robot-basedtape storage system at Caltech. Two ob-

serving sessions have been completed sofar, with two more to come in summer2001. The data processing is under wayand it is hoped to compare spectra fromdifferent observing runs in the near fu-ture. As an example, the emission andabsorption spectra towards PSRB2016+28 are displayed in Fig. 5. Thesewere obtained with about 30 min of in-tegration.

Studies of OH/IR Stars

Arecibo observations are making it evermore obvious that the 1612-MHz emis-sion phase of many OH/IR stars is verybrief — frequently little more than a fewhundred years. The most recent evidencecomes from accumulating statistics ontheir births and deaths, where MurrayLewis (NAIC) now has three instancesof each. The death of an OH/IR star (lossof all masers) is the easiest phase to reli-ably document. Moreover, these casesderive from the reobservation of just 250

stars over 15 yr in a summer studentproject. IRAS 18455+0448, which haspreviously been discussed in AO News-letter No. 30 as having an exponentiallydecaying maser, is no longer detectable.U Equ (alias IRAS 20547+0247), thesecond instance, is shown in Fig. 6 atthe three observed epochs: it has fadedfrom ~0.5 Jy to less than 6 mJy. Finally,IRAS 15060+0947, which was first de-tected in May 1985 with 143- & 370-mJy peaks, had a peak intensity of 15mJy last October. A normal amplitudevariation in intensity for 1612-MHzmasers around a pulsation cycle is by afactor of 2 – 3.

The birth of an OH/IR star is moredifficult to document, as a prior non-de-tection may have been caused by inter-ference, or by encountering the starduring a low intensity phase of its cycle:Murray has to read his old mildewedtapes to reach closure on this. Never-theless, the number of births presentlymatches the number of deaths, as expect-ed for a steady state population. So, inaddition to V1511 Cyg (see AO News-letters Nos. 28 and 30), Murray has re-cently observed 1612-MHz masers fromIRAS 18432+1343 (250 mJy, see Fig. 7)and from IRAS 18280+0521 (100 mJy).These masers are both strong enough thateven if they had been a factor of threeweaker when first surveyed, they shouldhave been detected during their previ-ous Arecibo search, made in May 1987and May 1988 respectively. MurrayLewis and Dieter Engels (Hamburg, Ger-many) detected water masers from bothstars at Effelsberg in 1994. These birthsstand apart from another 20 objects withnewly-recognized weak (~20 mJy) ma-sers, which are primarily detected at thistime due to increased sensitivity follow-ing simultaneous observations of the1612-, 1665- and 1667-MHz lines.

Murray has also been active in de-termining better positions for AreciboOH/IR stars. Most OH/IR stars in theArecibo sky have IRAS positions with atypical precision of order 10 arcsec.Now these can often be improved byidentifying their near-IR counterparts

Figure 5: The HI emission and absorption spectra towards PSR B2016+28 as recorded recorded using the

Caltech Baseband Recorder (Courtesy Snezana Stanimirovic)


from the 2MASS survey, where the typ-ical precision is ~0.2 arcsec. This wouldstill be impossible for most objects in theGalactic Plane without first identifyingthe Midcourse Spacecraft Experiment(MSX) counterpart, this having an inter-mediate precision of ~2 arcsec. DerekKopon, an undergraduate summer stu-dent from Cornell, together with Mur-ray & Yervant Terzian (Cornell), havethus succeeded in identifying the2MASS counterpart from 114 fieldsabout Arecibo OH/IR stars using extantpublic data. Fig. 8 is a plot of the result-ing K-band magnitudes against the ratioof the IRAS 25- & 12-µm flux densi-ties: the thicker the shell, the fainter themagnitude. Two objects appear discrep-ant: the reddest is the ambiguous objectIRAS 05506+2414 (BC Tau), situated atthe far right of the figure, which is ei-ther a proto-planetary nebula or a YSO.The bluer is IRAS 19453+1917, whichhas a secure identification with a muchfainter K-band magnitude than its IRAScolor would suggest, even though it isstill much brighter than the catalogthreshold of ~14.7. Perhaps, speculative-ly, this is the signature of a rapidly-thick-ening circumstellar shell.

An HI Survey of Dark Clouds

Previous l21-cm observations toward aselected sample of dark clouds by Di Li& Paul Goldsmith (NAIC & Cornell)yielded interesting and somewhat con-troversial results (see AO Newsletter No.29). These observers detected narrow,deep absorption features which are mostlikely associated with dark clouds. Thelarge amount of cold atomic gas inferredfrom the absorption optical depths re-quire a modification of the standard H

2

formation rate. Recent progress in grainmodeling, lab simulation, and grain sur-face chemistry corroborate this line ofthought. Di & Paul have run a H

2 forma-

tion simulation based on the most recentchemical rates. This demonstrates a slowdown of H

2 production at low HI densi-

ties, and can thus explain their observa-tions well.

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IRAS 18432+1343

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Figure 6: 1612-MHz spectra at three observed epochs for U Equ (alias IRAS 20547+0247). The upper panel

shows the observation of 8 May, 1988, while those of 24 April, 1999, and 25 December, 2000, are displayed inthe lower panel. (Courtesy Murray Lewis)

Figure 7: The 1612-MHz spectrum of IRAS 18432+1343 taken on 01 Jan, 2001. (Courtesy Murray Lewis)


Two aspects of the controversy stillremain. First, the location of the self-ab-sorption. A recent Canadian HI surveyusing the DRAO-ST detects large num-bers of cloud-like structures in absorp-tion, of which only 50% have known COassociations. The existence of cold HIcondensation in the solar neighborhoodhas been proposed. Second, is the atom-ic component associated with molecu-lar clouds exists in the envelope or isdistributed inside the clouds?

In the light of their analysis andthese competing views, Di & Paul haveextended their HI project into a surveytoward optically selected dark clouds.From Feb 1-3, 2001, they observed 36sources covering all starless cores in theArecibo sky with 0 hr < RA < 6 hr, andwith angular sizes of at least 2 arcmin.The observing strategy was to utilize thehigh sensitivity and spectral resolutionof the upgraded Gregorian system. HIand OH (1665 & 1667 MHz) were ob-served simultaneously with down to ~0.1kms-1 channel width. Only ON scanswere taken to avoid the uncertainty in-troduced by the variation in the back-ground HI emission. Out of 36 sourcesobserved, 29 have narrow absorptionfeatures with corresponding OH emis-sion lines in velocity space. Four of theremaining seven have the OH lines onthe slope of the λ21-cm emission, andthe effect of absorption is visible, but not

clear. Overall inspection attests to theprevalence of HI self-absorption associ-ated with dark clouds. They also sur-veyed two OFF positions at distances of10 and 20 arcmin for the 29 targets iden-tified above. Seventeen of these showsignificant reduction in HI absorptionand OH emission in the OFF positionsand therefore identify the HI self-absorp-tion as clearly associated with the darkclouds. L1544 is shown in Fig. 9.

In their HI spectra, absorption fea-tures unrelated to OH emission are of-ten present. However, any direction withmolecular emission will also have coldHI in the beam. This suggests a morecomprehensive view of the atomic ISM,with temperature fluctuations both asso-ciated with, and independent of, molec-ular cooling. The H2 formationsimulation of Di & Paul illustrates thatit is feasible to maintain a significantatomic component inside dark clouds.More studies involving models of pho-ton dissociative regions (PDRs) are be-ing conducted to address quantitativelythe issue of HI in the cloud envelope.

HI in High Latitude Clouds

The widths of almost all radio spectrallines from molecular clouds indicate thata substantial fraction of the moleculargas is undergoing suprathermal motion.Given this basic observation, the diffi-culty is in explaining how these suprath-ermal motions can be maintained overmolecular cloud lifetimes. In the past,ideas centering on long-lived MHD tur-bulence and a spectrum of Alfven waves

Figure 9: The HI self-absorption (black) and OH 1667-MHz emission (red, amplified 15-fold) are plotted inuncorrected antenna temperatures for the source L1544. The offsets are labeled on the individual plots as (ra,

dec) in arcmin. (Courtesy Di Li)

2

4

6

8

1 0

1 2

1 4

1 6

- 0 . 8 - 0 . 6 - 0 . 4 - 0 . 2 0 . 0 0 . 2

2MASS identifications for OH/IR Stars

Ks

(25-12) µm

Figure 8: 2MASS K-band magnitudes plotted against the ratio of the IRAS 25- &12-µm flux densities for 114 Arecibo OH/IR stars (Courtesy Murray Lewis)


were favored as the mechanisms bywhich a cloud could support itself againstwholesale collapse. In the last few years,numerical and analytical results haveshown that whatever the source of thesesuperthermal linewidths, the dissipationtimescale for waves or turbulence isshort, of order a dynamical crossing time.In the light of these computational re-sults, it is now clear that molecular cloudvelocity fields require a continuous en-ergy input if they are to be sustained overcloud lifetimes. Thus, a fundamentalproblem in understanding molecular

cloud structure is to identify the possi-ble sources for this energy.

One of the ways of externally inject-ing energy into a molecular cloud is viahigh-speed flows from large shock frontsin the ISM. If this is a ubiquitous fea-ture of non-star forming clouds, then oneshould be able to examine the surround-ing medium for the velocity signaturesof the shear flows. Loris Magnani (Geor-gia), Ted LaRosa (Kennesaw State) &Steven Shore (Indiana) chose to searchfor evidence of neutral atomic flows via

the λ21-cm HI line in the environs of anisolated, nearby, non star-forming, high-latitude molecular cloud (MBM16).Without the complication of galactic ro-tation or long sight-lines through thedisk, the HI velocity field in the vicinityof the target cloud is simpler to analyzethan that of HI disk clouds. Althoughthe analysis has just begun, the filamen-tary HI structures evident at variouschannels in the 2.5 × 4 deg map (see Fig.10 for examples) seem promising. Theseobservers will compare their HI data withCO data for this molecular cloud (whichcovers about 6 square degrees in the mid-dle of the HI map) and see if a relation-ship between the atomic and moleculargas at differing velocities can be deter-mined. The Arecibo telescope is the onlyinstrument in the world that has suffi-cient resolution of extended gas to allowthe detailed HI-CO comparison that isneeded in order to establish the presenceof high-speed atomic flows.

High Velocity Gas in M61: A TidalTail?

Recent HST observations detected aMgII doublet in absorption along a lineof sight through the outskirts of M61 to-wards a radio-quiet QSO (Bowen et al.,1996, ApJ, 472, L77). The MgII absorp-tion lines show a two-component struc-ture, one that is associated with the diskof M61, and a surprising blue-shiftedwing which cannot be explained as partof M61’s rotation. Such complex absorp-tion line structures are commonly seenin higher redshift systems, but for thesesystems detailed information on the dis-tribution and kinematics of the gas is notavailable. Fortunately, low redshift sys-tems, such as M61, provide an opportu-nity to investigate the nature of the gasin much larger detail.

Rob Swaters (DTM, Carnegie Inst.),Wendy Lane (NRL) & Frank Briggs(Groningen) used follow-up VLAobservations to obtain the distributionand kinematics of the HI. At the positionof the quasar, they detected largeamounts of HI, but only at velocities that

Figure 10: Example 2.5° × 4G° channel maps of the high-latitude molecular cloud, MBM16, for v = -4.2, -1.0

and 2.3 km s-1. They demonstrate the presence of considerable filamentary HI structure. (Courtesy Phil

Perillat)


correspond to that of the disk. No gaswas detected at anomalous velocities.However, no HI is seen along the QSOsight-line at the velocity of the blue-shifted absorption seen in MgII. The datado provide other clues, which suggestthat the blue-shifted absorption is causedby a Magellanic Stream-typephenomenon: there is widespread highvelocity gas still connected to the diskof M61, to the north is a low mass (~106

M�) HI cloud that may be a condensationwithin the hypothesized Stream, and thedwarf companion to M61, NGC 4301,is clearly elongated towards M61. Allthese features are continuous in velocity,and together suggest that a close passageof NGC 4301 to M61 has created aMagellanic Stream-type feature.However, they leave open the possibilitythat this HI gas is part of a halo of highvelocity clouds.

Hoping to discriminate betweenthese possibilities, this team used theArecibo telescope to detect HI associatedwith the blue-shifted wing seen in MgII,and the tidal feature. A preliminaryanalysis shows a detection of the blue-shifted component in HI, at a columndensity of a few times 1017 cm-2. In thedisk of M61 there is evidence for highvelocity gas, but they do not see any HIin emission between M61 and NGC4301, except at the position of the HIcloud already detected in the VLAobservations. However, some of this gasmay be at velocities of either M61 orNGC 4301. If that is the case, itsemission could easily be masked bysidelobe contamination due to M61 andNGC 4301.

HI in the Most Luminous Post-Starburst Galaxy in The LocalUniverse

The “E+A” (“Elliptical + Active” =post-starburst) galaxy, G515, discoveredby Oegerle et al. (1991) is a veryluminous object (MR = -23.1) which hasbeen shown to contain a stellarpopulation consistent with a massive,global starburst 1-Gyr old (Liu & Green1996). Furthermore, it contains no

ionized gas that would indicate on-goingstar formation; yet it has significant far-infrared luminosity implying thepresence of gas and hot dust. Thus, itmay be the most interesting example inthe local Universe of a galaxy’s transitionfrom late-type to early-type after aninteraction or merger. To determine theneutral hydrogen content of thisremarkable galaxy, and thereby provideinsight into the relation between the HIcontent and post-starburst phase ofgalaxies, Charles Liu (AmericanMuseum of Nat. Hist.) & Karen O’Neil(NAIC) recently observed G515 withArecibo. The galaxy was not detected,but preliminary results place an upperlimit of MHI < 6 × 108 M� on the system.

Hunting for Massive Galaxies

One of the more extreme ends of thedisk galaxy sequence are the massivelow surface brightness spiral galaxies,the prototype of which is Malin I. Theseare characterized by large scale lengths,low central surface brightnesses, and(typically) high neutral hydrogenmasses. In addition to being fascinatingin their own right, the slow star formationrates of these galaxies allow us a uniqueview into the conditions that likelyexisted during the formation of many ofthe massive (HSB) galaxies we seetoday, as well as being importantcontributors to the total baryon mass ofthe local Universe.

In an effort to learn more about thesefascinating objects, two groups havebeen working at Arecibo to identify mas-sive LSB spiral galaxies. Karen O’Neil(NAIC) & Greg Bothun (U of Oregon)recently completed a survey of UGCgalaxies whose morphologies are indic-ative of a high gas content, yet whichhave not been detected previously inλ21-cm searches out to 10,000 km s-1.In all, 50 galaxies were observed, andHI detected in 27. The detected galax-ies range in velocity from 760 km s-1

(dwarf systems overlooked in previoussurveys and found now because of Areci-bo’s increased sensitivity) out through30,200 km s-1, with the majority lying

between 13,000 and 20,000 km s-1 away.Perhaps the most impressive find withthis survey is UGC 4288. Previously thisgalaxy was believed to be a nearby dwarfgalaxy with HI mass less than ~107 M�.However, Karen & Greg have found itto lie at a distance of 30,220 km s-1, witha HI velocity width of ~570 km s-1 anda HI mass of 5.2 × 1010 M� (see Fig.11).

In similar vein, Jim Schombert (U ofOregon), Karen O’Neil (NAIC), & JoAnn Eder (NAIC) are using the DigitalPalomar Sky Survey (DPOSS), com-bined with the 2-Micron All Sky Survey(2MASS) to identify massive low sur-face brightness galaxies that were notpreviously identified in other sky sur-veys, and whose morphologies are sug-gestive of Malin 1-class objects.Preliminary results from this survey havefound more than fifteen of these objects,dramatically increasing the number ofmassive, low surface brightness galax-ies known.

HI in a Damped Lyman-ααααα Absorber

Nissim Kanekar (NCRA, India), TapasiGhosh (NAIC) & Jeyaram Chengalur(NCRA) have made high-resolutionArecibo λ21-cm observations of thedamped Lyman-α absorber (DLA) to-wards the quasar OI~363. The Arecibospectrum yields a spin temperature Ts =890 ± 160 K, consistent with earlier low-er sensitivity observations of the system.This value of Ts is far higher than spintemperatures measured for the Milky

Velocity (km/s)

UGC 4288

0

2

4

Flux

den

sity

(m

Jy)

30,200 31,40029,200

Figure 11: The HI spectrum of the galaxy, UGC4288. (Courtesy Karen O’Neil)


Way and local spirals, but is similar tothose obtained in the majority of dampedabsorbers (Ts >1000 K). For a multi-phase medium, the measured spin tem-perature is the column density-weightedharmonic mean of the temperatures ofindividual phases. Hence, Nissim andJeyaram had conjectured earlier that thehigh Ts of the z = 0.2212 absorber andthe majority of other DLAs could be ex-plained if they were systems like dwarfsor LSB galaxies which contain largerfractions of the warm phase of HI(WNM), as compared to local spirals.

The high velocity resolution of theArecibo spectra (Fig. 12) enables themto obtain estimates of the physical con-ditions in the absorbing clouds by fittingmultiple Gaussians to the absorption pro-file. The spectra are well fit by a three-component model with two narrow andone wide components having tempera-tures, Tk1 = 308 ± 24 K, Tk2 = 180 ± 30K, and Tk3 = 7600 ± 1250 K, respec-tively. The last of these is in excellentagreement with the expected tempera-tures for the WNM (5000-8000 K). Fur-ther, the mere fact that components areseen with much lower temperatures than

the estimated Ts implies that the absorb-er must have a multi-phase medium.

They use the measured λ21-cm op-tical depth and the above estimates ofkinetic temperature to obtain the HI col-umn density in the various components.The total column density in the narrowcomponents is found to beNHI(CNM)<1.9 ± 0.25 × 1020 cm-2,while that in the wide component isNHI(WNM) > 1.26 ± 0.49 × 1021 cm-2.Thus, the WNM contains at least 75%of the total HI in the z = 0.2212 DLA,unlike our Galaxy in which the CNMand WNM have equitable contributions.As Nissim and Jeyaram conjectured ear-lier, this accounts for the difference inthe spin temperatures of the z = 0.2212system and local spirals, suggesting thatthe DLA is probably a dwarf or LSB typegalaxy. Further, this is also in agreementwith optical studies by Turnshek et al.(2001). Finally, the total column densi-ty in the DLA is found to be NHI~1.45 ±0.49 × 1021 cm-2, which agrees withinthe errors with the value of NHI = 7.9 ±1.4 × 1020 cm-2, obtained from the Ly-man-α profile by Rao & Turnshek(1998). This reinforces the identification

[A] [B]

[C] [D]

Figure 12: The Arecibo 0.4-km s-1 resolution λ21-cm absorption spectrum of the z=0.2212 absorber towards OI 363. The panels are as follows; [A] The spectrum

(open squares) with the three-component Gaussian fit (see text) shown as a thin solid line; [B] A zoomed-in version of panel [A] to bring out the shallow absorption

wing; [C] Residuals after subtracting the two narrow components from the spectrum (open squares). The fit to the wide component (see text) is shown as a thin solidline; [D] Residuals after subtraction of the two narrow components and the wide component from the spectrum. (Courtesy Tapasi Ghosh)

Space and Atmospheric Sciences

Don Farley

On-line ISR Database

You can now access Arecibo incoherent scatter radar data directly from

the NAIC web site. Just click on Scien-tific Users, then Space and AtmosphericSciences, then the ISR database link.Follow the menu directions to get cus-tomized plots of Arecibo data. The plotsare generated on line allowing great flex-ibility, although it takes some time to readand plot the data. Users can adjust thescales of color images or click on animage to get a time series for a particu-lar height or height profile for a particu-lar time. Currently not all the data listedin the menu is actually available, but weare working to get everything into theproper format as soon as possible. Thereare also links to descriptions of the WorldDay data and the various analysis pro-

of the wide and narrow components asthe WNM and CNM respectively.


grams. Try this out and let us know aboutany problems.

Optical Database

There have been links to some of the li-dar data for some time. We are workingto make more of these observationsavailable. At present, these consist ofcolor range-time plots of Na and K den-sities. These are the same plots that canbe viewed with the real-time data moni-tor that runs during experiments. (URL:h t t p : / / w w w. n a i c . e d u / ~ l i d a r /realtime.html)

430 MHz Dual Beam Radar Measure-ments

Dual-beam 430 MHz radar was dis-cussed at some length in the previousNewsletter. At the time of this writing,we still cannot quite make these mea-surements, but we are tantalizingly close.We had a failure in the high power col-lector for the Gregorian feed (the devicethat takes the 430 MHz transmitter pow-er out of the slotted waveguide). Thisdevice had worked before, and we un-derstand what caused the failure, so it isnot a major problem, but it has delayedother final tests by 2-3 weeks. Very re-cently the revised data taking hardwareand software needed for the dual beamsystem were successfully tested, as de-scribed below.

Aeronomy Data-Taking

We have successful tested the new rawdata transfer capability for the aerono-my data-taking system. We can nowsample and process data from the linefeed and the Gregorian simultaneously.The current radar interface does the sam-pling, and a new card in the VME cratereceives the data and transfers it to a dualprocessor 850 MHz Linux PC where itis stored on disk and processed. Othercomputers on the local area network canalso access and process the data. Therecent test ran in exactly the mode re-quired to make velocity, temperature,and composition measurements in the F

region using both radar feeds. It usedonly about 20% of the transfer capabili-ty of the entire system, and so there isroom for future applications. The data-taking software running on the VMEcrate is a new version of the “MRACF”program, which now samples two re-ceivers rather than one and sends the datato the PC for processing rather than us-ing an array processor in the VME crate.

We have developed a Linux versionof the program that processes the rawdata, and we are now writing the specif-ic processing modules which duplicatethe computation that occurred in the ar-ray processor. There will be one of thesefor each of the current data-taking pro-grams, allowing a direct comparisonbetween results taken with the old andnew systems. Once these comparisonsare complete we will develop improve-ments to the software that will take ad-vantage of the increased computingpower and flexibility.

Separating the system into a real-time sampling part and a computing partwill make future upgrades easier; we canswitch to faster PCs as they becomeavailable, for example. However, sincevirtually identical programs exist forLinux PC, Sun OS and Mac OS X, al-most any computer can be used, includ-ing a laptop brought by a visitor.

We can also upgrade the samplingpart of the system, for example with dig-ital sampling receivers. The idea is tosample and digitize directly at the RF,or more likely some IF, and do all thesubsequent filtering and mixing digital-ly, eliminating the current analog filtersand complicated cable setups. Existingtechnology may or not be adequate forour needs, but there is little doubt that ifnot now, it will be soon.

Ionospheric Interactions

Two separate studies of the HF feed sys-tem discussed in the previous Newslet-ter have now been completed and areessentially in agreement. The 2-elementYagi scheme of feeding the main dish is

feasible. We are now trying to get de-tailed cost estimates for both this feedsystem and also for the transmitter, ei-ther a new transmitter (the preferred op-tion) or rebuilding the old ones. A newtransmitter would be more reliable andmuch easier and less costly to maintain,but the price estimates that we have sofar are considerably higher than wewould like. We are very close to havingan estimate of the (not un-substantial)cost of rebuilding the old transmitters andthe time required to do it.

430 MHz Klystron Status

The rebuilt klystron, after a rather shakystart, has been performing better andbetter as we use it. It now puts out some-what more power than the otherklystron—the one that didn’t fail. Thisperformance is very encouraging andsuggests that we can successfully rebuildother klystrons for $60K or so each ifthey should fail.

Electron Collision Effects

Turning now to science, some niceprogress has been made on the questionof how electron collisions affect the the-ory of incoherent scatter when the radarbeam is nearly perpendicular to the mag-netic field. This work is relevant to mea-surements at Jicamarca, not Arecibo, butMike Sulzer and Sixto González (bothNAIC) have developed a theory, via arather complicated numerical simulation,that appears to explain the effects at Ji-camarca that have been a puzzle formany years. This puzzle was that, afterfitting the observations to the “standard”ISR theory, the analysis often impliedthat the Te/Ti ratio was less than unity,which is a physically unreasonable re-sult. This was true even though the mag-netic field was taken into accountproperly, and even if electron collisioneffects were included via a simple BGKor Fokker-Planck model. Most effortsat Jicamarca were devoted to looking forsubtle systematic errors introduced intothe data by electrojet and/or satellite clut-ter or some other cause. These latter ef-


fects do tend to produce the same sort ofeffect on the deduced Te/Ti, but it hasnot been possible to explain the prob-lems seen well above the F-region peak,especially, in terms of systematic errors.

Sulzer & González, in a 1999 paper,pursued the idea that there really wassomething wrong with the incoherentscatter plasma theory, or at least the partof it that deals with electron Coulombcollisions. The BGK model is pretty re-alistic for binary collisions betweencharged and neutral particles, but longrange Coulomb collisions are more com-plicated. The dependence on particlevelocity is not very well modeled, evenby the Fokker-Planck model; at least thatwas the suspicion of Sulzer andGonzález. They developed a Monte-Carlo simulation that accurately calcu-lates the electron admittance function,taking account of how electrons of a par-ticular velocity are affected by both elec-tron-ion and electron-electron collisionsand then summing over all velocities.The Fokker-Planck model, in contrast,

uses a single collision frequency param-eter for all particle velocities.

The simulation must be run many,many times to build up a “library” of the-oretical curves for the appropriate rangeof values of electron density, electrontemperature, and angle between the ra-dar k (line of sight direction) and theearth’s magnetic field. Such a library isnow available, and it has been incorpo-rated into an incoherent scattering least-squares-fitting code.

Using the new theory, Néstor Apon-te (NAIC) processed Jicamarca ACFdata obtained using the Faraday/ACFmode. A sample of the results is shownin Figure 13, in which the Te/Ti ratio isplotted as a function of altitude for threedifferent antenna pointing positions. Inthis plot, the terms ‘on-axis’, ‘4 degrees’,and ‘6 degrees’ have been used looselyto refer to the different antenna pointingpositions. The on-axis position is theclosest to perpendicular to the earth’smagnetic field (B), less than 2° at 400km (an angle that varies slightly with

altitude). The 4° and6° positions pointfarther away fromperpendicular to B,with the 4° positionbeing between 3.6°and 3.2° from B andthe 6° position beingbetween 5.1° and4.5° from B between250 and 550 km.Each panel containsa curve obtained byfitting the radar datato the standard mod-el without electronCoulomb collisions(blue line) and acurve obtained fromthe new Sulzer &González model thatincludes the effectsof collisions (redline).

The effect of thecollision correction

is largest for the left panel, for which thebeam is closest to perpendicular to B,and least for the right panel. (We shouldmention also that the right panel corre-sponds to an antenna pattern with largesidelobes and the most serious cross-talkand clutter problems.) The corrected(red) curves do a nice job of eliminatingvalues of deduced Te/Ti less than unityabove 350 km or so. We should men-tion that using a BGK or Fokker-Planckmodel, instead of the Sulzer & Gonzálezsimulation, would make corrections inthe same sense, but not nearly as largeas the corrections shown, leaving de-duced temperature ratios still significant-ly less than unity, which cannot becorrect.

So it appears that this new theory re-ally does explain the Jicamarca ISR re-sults. This theory may have widerimplications; there are no doubt otherplasma phenomena involving electronCoulomb collisions for which the colli-sion effect has been underestimated.

Optical Observations

Airglow observations were included dur-ing World Day experiments in Decem-ber (a 4-day, Lower ThermosphericCoupling Study) and in a 3-day run inJanuary. The data collected consisted ofthermospheric neutral winds from Fab-ry-Perot interferometry (FPI) and air-glow intensities, primarily of the atomicoxygen O(1D) and Hα emissions.

We participated in Bob Kerr’s (Sci-entific Solutions) and Néstor Aponte’s(NAIC) experiments in January, in whichfour nights of radar observations plus ap-proximately 10 nights of optical mea-surements were made. A description ofKerr et al.’s observations is given below.Aponte and co-workers examined the ionenergy balance of the thermosphere. Aswith the World Day studies conductedthis quarter, to support this work we ob-served the thermospheric winds by mea-suring the O(1D) 630 nm airglow, as wellas exospheric Hα (656.3 nm) emissions.The nights were generally clear and thedata quality was very good for these

Big Effect Medium Effect Small Effect

0 1 2 3

200

300

400

500

14:03 LT

1997/8/27

Te/Ti 0 1 2 3

20:00 LT

1998/3/25

Te/Ti 0 1 2 3

14:39 LT1997/8/28

Te/Ti

on-axis 4.5 deg 6 deg

km

CC

No CC

Figure 13: The Te/Ti ratio at Jicamarca for three different antenna posi-tions. In all panels the blue line comes from fits with the standard theory,

while the red line was obtained from fits with the theory that includes the

effect of Coulomb collisions. Left panel: on-axis position August 27, 199714:03 LT. Center panel: “4.5 deg.” position March 25, 1998 20:00 LT.

Right panel: “6 deg.” position August 28, 1997 14:39 LT. (Courtesy Néstor

Aponte)


studies, as well as for those during theWorld Day experiments.

An ongoing initiative to measure thecomposition and dynamics of the upperthermosphere, exosphere, and topsideionosphere was served during the peri-od January 14 – January 27. Bob Kerrand Yan Betremieux of Scientific Solu-tions Inc. (SSI), North Chelmsford MA,were assisted by Jeffrey Hyland ofTewksbury Memorial High School andSSI for the optical and infrared measure-ments that this program features. Thevisitors used two Fabry-Perot interfer-ometers to measure the OI 6300 Å emis-sion and the Hα 6563 Å emission,providing winds near the F2 peak andthe exospheric H velocity distribution,respectively. Two photometers and theEbert-Fastie Spectrometer were also op-erated. The photometers measured theOI 8446 Å and the Hα nightglow bright-ness, providing diagnostics for (photo-electron model dependent) Ocomposition in the upper thermosphereand the column abundance of exospher-ic H, respectively. An example of Hαphotometer data is shown in figure 14,and preliminary analyses indicate that at20% enhancement of H column abun-dance occurred following a magnetic dis-turbance that began on Jan. 20. Theperiod was characterized by excellent

optical viewing con-ditions throughout,and the Hα data willbe a valuable addi-tion to a long termstudy of globalchange in atmospher-ic hydrogenous com-position. Use of thenested optical instru-mentation in concertwith the topside 430MHz radar measure-ments provides aunique sample of allsignificant speciescompositions and allphysically significantdynamics in the up-per thermosphere,exosphere, and top-

side ionosphere—for the purpose of un-derstanding the coupling between theseatmospheric regions.

During January 2001, we measuredthe Rayleigh signal backscattered fromthe neutral atmosphere up to about 90km altitude using our Nd:YAG laser and

Figure 14: The Hα column emission measured in the post-midnight pe-riod of January 22 is illustrated. These data were taken following a mag-

netic disturbance that began 48 hours earlier, and indicate a 10% – 20%

enhancement of H column abundance above Arecibo as a consequence ofthe disturbance. (Courtesy Bob Kerr)

0.8 m telescope. Nightly temperatureprofiles were estimated from these databy measuring the slope (scale height) ofthe neutral density profiles. These areshown in Figure 15 for 5 nights and theiraverage between January 17 and 24. Us-ing our resonance fluorescence Dye andAlexandrite lidars we also measured thereturns from the sodium and potassiumresonance lines, respectively. These me-tallic atoms are distributed between 80and 100 km by meteor ablation. Partic-ipants in these studies were Rubén Del-gado (University of Puerto Rico-RíoPiedras), and Jonathan Friedman, ShikhaRaizada, and Craig Tepley (all of NAIC).Overall, about two weeks of nearly con-tinuous lidar data were collected duringthis January period.

30

40

50

60

70

80

90

Alti

tude

(K

m)

Temperature (K) Temperature (K)

150 300 150 200 250 300

17-18 18-19 19-20 22-23 23-24

JANUARY, 2001

5 day average

(a) (b)

Figure 15: Nightly and average temperature distribution of the middle atmosphere for January 2001deduced from Rayleigh lidar. Shown are (a) Temperature profiles compared to the MSIS-90 model (dashed

line) for 5 winter nights, and (b) the ‘monthly’ average temperature altitude profile. Deviation below

about 35 km is due to the fact that the telescope and laser fields-of-view are not completely overlapped inthis bi-axial system. (Courtesy, Shikha Raizada)


Solar System Studies

Don Campbell

The combination of the improvedsensitivity of the Arecibo 13 cm

wavelength planetary radar system andthe increased rate of discovery of nearearth asteroids means that the radar sys-tem is under very heavy demand. Thefall of last year saw a series of observa-tions of Titan, an attempt to detect an-other satellite of Saturn, Iapetus,observations of the Galilean satellites ofJupiter, delay-Doppler imaging of therings of Saturn, imaging observations ofnumerous near earth and main belt as-teroids and additional imaging observa-tions of the moon at both 13 cm and 70cm. Through early March of this yearthere have been observations of a num-ber of near earth and main belt asteroidsand a series of bistatic runs on Venuswith Arecibo transmitting at 13 cm andseveral antennas at the NASA/DSNGoldstone facility receiving the echo.

The Titan observations by G. Black(NRAO), D. Campbell (Cornell/NAIC)and S.Ostro (JPL) confirmed the mea-sured values of the average scatteringproperties of Titan made in the fall of1999. However, the major objective ofthe observations was to measure Titan’sscattering properties as a function of lon-gitude. The longitude of Titan’s sub-earthpoint moves approximately 22 degreesper (earth) day. Observations werescheduled in two groups giving full lon-gitude coverage at this 22 degree spac-ing. Unfortunately, only about half thelongitude coverage was obtained due totransmitter problems. Little variationwas seen in the scattering properties butthe covered region did not include thelongitudes where a bright feature hasbeen observed in near infrared imagingby the Hubble Space Telescope andground-based telescopes using adaptiveoptics systems. On two days there weresuggestions of a quasi-specular compo-nent to the echo but confirmation of thiswill have to await new observationsplanned for the fall of this year.

P. Nicholson (Cornell) and otherspursued their study of azimuthal asym-metries in the optical and radio wave-length scattering properties of the ringsof Saturn. Delay-Doppler images of therings were obtained with a range reso-lution of approximately 10,000 km, highenough to separate the echoes from theA and B rings.

There was major excitment at thediscovery in the fall that two recentlydiscovered small near earth asteroids,2000 DP107 and 2000 UG11, are bina-ry systems. The discoveries involvedobservations with both the Arecibo andGoldstone radar systems. While therehave been suggestions from optical ob-servations that some near earth asteroidsare binary systems, these are the firstconfirmed detections. The people in-volved in these observations were J-L.Margot (NAIC, now at Caltech), M.Nolan (NAIC), L. Benner, S. Ostro, J.Giorgini (JPL), S. Hudson (WSU) andD. Campbell (Cornell/NAIC). BothDP107 and UG11 were very recent dis-coveries and there was no indicationfrom the initial optical observations thatthere was anything very unusual aboutthem. This highlights the importance ofusing the radar to observe as many ofthese small objects as possible and theasteroid radar community is very grate-ful to those users of the telescope whoare willing to sacrifice some of theirobserving time on short notice to makethese observations possible.

With the improvements in the rmssurface accuracy of the telescope’s pri-mary reflector, the overall sensitivity ofthe 13 cm radar system is approachingthe original goal of the recent telescopeand radar system upgrading project. Theresetting of the 1900 tie down cables ofthe reflector has increased the 13 cm gainby approximately 20% and made it muchless dependent on the zenith angle andazimuth of the Dome. The resetting ofthe individual panels of the reflector,expected by the end of 2001, should givea further 15% increase in the gain. Thisincrease in gain has been accompaniedby other system improvements. Due to

the efforts of Tony Crespo and VíctorNegrón the transmitter is now more reli-able than in the past and Phil Perillat andMike Nolan have made the data acquisi-tion software extremely dependable andflexible. The portable fast data acquisi-tion system developed by Jean-Luc Mar-got with the help of Jeff Hagen hasenabled very wide bandwidth data acqui-sition at Arecibo and bistatic observa-tions with the St Croix VLBA antennaand, soon, the 100m Green Bank tele-scope. A copy of this system has beenbuilt for use at the 70m NASA/DSNGoldstone antenna.

Computer Department News

Arun Venkataraman

Internet 2 getting closer

Following the award to Centennial PRand Qwest Inc of the contract to build

the PRISA (Puerto Rico Internet 2 Ser-vices Association) on-island OC-3 net-work with DS-3 uplink to the Abilene I2backbone, work has begun on the fiberlayout for the Observatory’s “local loop”in the teeth of right-of-way permit diffi-culties faced by Centennial. Florida In-ternational University’s GigaPOP,managed by FIU’s AMPATH Project,will provide PRISA’s actual link to I2.The Observatory’s central router hasbeen upgraded to support the 155-Mbits/s ATM/SONET interface to Centennial’son-island ATM network. The router willalso channel non-I2 traffic into the Ob-servatory’s existing T1 link to the com-mercial Internet.

Control Room observing

While a faster network connection canmake the remote observing option attrac-tive in the foreseeable future, the newobserver’s workstation in the ControlRoom is worth a visit. This is currentlya Sun Ultra-60 with 1GB RAM, dual dis-plays (one of them a flat-panel LCD) anda gigabit ethernet connection to the net-work servers. And while old-time Ob-servatory hands can still use the


venerable Analyz data reduction envi-ronment (now in its silver jubilee year),new reduction software is being writtenfor the Research Systems Inc. IDL envi-ronment, notably the calibration andmapping routines authored by Phil Pe-rillat and Dr Carl Heiles of UC Berke-ley and integrated with the UserInterface. Mike Nolan’s data conversionroutines support FITS and CLASS for-mat data export; CLASS users can mon-itor the exported data in realtime.

Data acquisition

The VMEbus continues to serve theObservatory well for basic control anddata acquisition, however, it has beenapparent for several years that the 32-bit bus would not be sufficient for high-end data acquisition applications;moreover, the processing power avail-able on the Observatory VMEbus ma-chines is exceeded by modern desktopworkstations. As earlier newsletters havereported, Intel-based PC’s running theLinux OS have been used for some re-cent data acquisition projects, notably theWideband Arecibo Pulsar Processor(WAPP); these machines feature PCIbusbandwidth and near-1GHz CPUs. Sincethe custom-built VMEbus componentsused to drive the Observatory’s radarsystem are expensive to duplicate, a hy-brid approach using components fromboth the VMEbus and the WAPP systemswas used by Bill Sisk, Jeff Hagen andPhil Perillat to build a data acquisitionsystem for dual-beam radar. The “glue”is provided by a custom-built IndustryPack I/O card that transfers data from aVMEbus single-board computer to thePCIbus computer.

Visitors LAN’ed at Observatory

The planned extension of the Observa-tory Local Area Network (LAN) to theVisitors’ Quarters should provide wel-come relief for guests who like to stay“connected” at all hours.

Employee of the year 2000

Daniel R. Altschuler

Another year has gone by and weagain had the difficult task of

choosing the Employee of the Year. Acommittee chaired by Carmen Segarraand composed by Víctor Santiago, JoséChacón, Antonio Nolla (all former re-cipients of the prize) and Julio Cresporeviewed the nominations by fellowemployees and came up with Víctor Igu-ina as the winner of this year’s award.

Víctor, has distinguished himself asa tireless worker in the Electronics de-partment where his hard work, expertiseand dedication have maintained the 430MHz transmitter so well that its excel-lent reliability is taken for granted by itsusers. Víctor has been with the transmit-ter from the start in 1964, first as a tech-nician with Domingo Albino, thetransmitter engineer, and then since 1992alone as engineer and technician. At thesame time Víctor has also contributedto the installation of fiber optic and tele-phone lines throughout the Observatory

Víctor is always ready to lend a help-ing hand, both on the job and off; he can

Víctor Iguina receives the award for Employee of the Year, 2000 from

Daniel Altschuler. (Photo by Tony Acevedo)

often be seen troubleshooting an auto-motive electrical problem for a fellowemployee.

The Arecibo Observatory, a SchoolScience Project

Jesse Stinebring

Arecibo Observatory is in PuertoRico. I decided to focus on how it

works and runs. I did some research onwhat it studies but not much on the his-tory. My dad is a scientist, and so he goesdown and works in Arecibo. That is howI decided to study the telescope for theIndependent Studies Project. I could takepictures and have interviews in Areci-bo. Arecibo is the biggest (and best) ra-dio telescope in the world.

I hoped to learn how the Arecibo tele-scope works, some of the measurementsof Arecibo (I got a lot of them), whatArecibo scientists study, and the historyof the Arecibo Observatory. I learnedall I wanted to learn. I got more of themeasurements than I expected. At thebeginning of my project, I thought Areci-bo only studied pulsars, stars, and plan-ets.

I didn’t have toomuch information,but what I had wasvery good. I had onegood book, one website, and lots of peo-ple let me interviewthem when I wentdown to Arecibo.When I went toArecibo, I saw all ofthe different parts ofthe telescope andhow the observatoryworks. It was verydifficult at the begin-ning of the projectbecause I had so lit-tle information. Butwhen I went toArecibo, I got a lotmore information.


Arecibo is the biggest radio telescopein the world. The dish is 1,000 feet (305meters) in diameter. It has a depth of 167feet (51 meters). The reflector’s surfacehas 38,778 aluminum panels. Arecibocovers 18 acres (8 hectares) or the sameas 26 football fields. Each concrete tow-er has 9,100 cubic yards of concrete. Twoof the towers are 265 feet (80.772meters) tall and the other tower is 365feet (106.68 meters) tall.

The Arecibo Observatory studies lotsof different things. It studies the planets,the ionosphere or atmosphere, pulsars,galaxies, quasars, and hydrogen gas inour galaxy. Arecibo has a program thatis called SERENDIP which stands for

S earch for

E xtraterrestrial

R adio

E missions from

N earby

D eveloped

I ntelligent

P opulations.

SERENDIP is a program that uses anantenna that sits at the top of the plat-form, but they haven’t found anythingyet!

Up 450 feet (137 meters) is the plat-form, and on it is a bow-like structure. Itholds the Gregorian dome and the car-riage house. The bow, or the azimutharm, is 304 feet (93 meters) long. Theplatform has 26 motors to move the azi-muth arm, the Gregorian dome, and thecarriage house to any position within amillimeter precision. The Gregoriandome is six stories high and weighs 75tons (68 metric tons), but the whole plat-form weighs 900 tons (803.6 metrictons).

The Arecibo telescope is in PuertoRico. The scientists and engineers whoplanned Arecibo were thinking of put-ting the telescope in Cuba or Hawaii, butthey decided to put the observatory in

Puerto Rico because there were sink-holes that they could put the dish in sothey didn’t have to blast so much. Eventhough they put the dish into a sinkhole,they still had to use a lot of blasting. TheArecibo Observatory is near the town ofArecibo, so if it was placed in Hawaii orCuba it wouldn’t be named the AreciboObservatory. The observatory of Areci-bo is way up in the mountains of PuertoRico so it is a long and bumpy drive toget there.

There are many jobs at Arecibo, sothey need lots of people working there.There are lots of jobs the workers haveto do like clean the dish of trash, fixthings on the platform, go under the dishto fix cables, and make sure everythingis going well in the control room. If youare under the dish and you hear a big,loud siren noise, that means you have toget out of there within 30 minutes be-cause the scientists are going to makemicrowaves to bounce off of differentobjects in the solar system. If you are upon the platform and you hear another si-ren (that’s not as loud as the first), thatmeans you have to get out of the way in5 seconds because the scientists are mov-ing the azimuth arm. The telescope op-

erator’s job is to make sure that the tele-scope is running well and to make surethat all of the 200 scientists who visitArecibo each year get their turn on thetelescope.

I started out by going on the comput-er and finding information on Arecibo.On December 27, 2000, my Dad flewdown to Arecibo to do research on pul-sars. On December 31, 2000, the rest ofmy family flew down to Arecibo to goto Puerto Rico for a vacation, to visit myDad, and to do my Independent StudiesProject. I asked a lot of people if I couldinterview them, and they all said yes. Iinterviewed the director of the observa-tory, two telescope operators, the direc-tor of scientific staff who is also a radioastronomer, and a scientist who uses LI-DAR (a kind of laser) to study the atmo-sphere and ionosphere. I went under thedish and got some pieces of the reflec-tor’s metal panels. I was going to go onthe platform, but we ran out of time togo on it. I was sad that I couldn’t go onthe platform, but I was also very relievedbecause the platform is very high up(even though nobody has died up thereand it is very safe). I am very glad I didthis project because I have been embar-

Jesse in front of his exhibit which includes this article plus a model of the Arecibo telescope he made. (Photo

Carter McAdams)


rassed that I do not know a lot about as-tronomy and radio telescopes. Thisproject has helped me learn what astron-omy is and how the biggest and best ra-dio telescope in the world works andruns.

Jesse Stinebring is a fourth-grade stu-dent from Prospect School Oberlin,Ohio. Jesse has visited the observatorytwice during the last three years alongwith his parents Dan and Lynn as partof Dan's regular observing program atthe telescope (see contribution to theradio astronomy article in this issue).Jesse wrote this article for his Indepen-dent Studies project and, at the time ofwriting, is currently “defending his the-sis” back in Oberlin.—Ed.

over lunch. The visiting party consistedof Ron Anderson, Floyd DesChamps, Dr.Robert Palmer, Karen Pearce andStephen Philip Johnson.

Ron Anderson is a Republican Ap-propriations staffer for Chairman JamesT. Walsh, chair of the house VA/HUDand Independent Agencies Appropria-tions subcommittee, the subcommitteewith jurisdiction over NSF spending.Floyd Deschamps is a Republican Pro-fessional staff member with the subcom-mittee on Science, Technology andSpace of the Senate Committee on Com-merce, Science and Transportation. TheCommerce, Science and TransportationCommittee is one of two authorizingcommittees with jurisdiction over NSFin the Senate — the other two being theHealth, Education, Labor and PensionsCommittee. Robert Palmer is the Dem-ocrat Democratic Staff Director for theHouse Science Committee. The ScienceCommittee is the only authorizing com-mittee on the House side with jurisdic-tion over NSF. Karen H. Pearce is aLegislative Policy Analyst at the NSF’sOffice of Legislative and Public Affairs.Stephen Philip Johnson is Assistant VicePresident for Government Affairs at

Visit from congressional staffers

Chris Salter

On Feb 20, John Harmon and myself hosted three “Congressional

Staffers”, plus an NSF representative anda Cornell Vice President. The visit in-cluded a tour of the control room andthe visitor center, as well as informal dis-cussions with scientific staff members

Colloquia since the last Newsletter

16 Feb, 2001 Abel Mendez, UPR, Col-loquium: Arecibo Planetary HabitableZones: The Spatial Distribution of Lifein Planetary Bodies

7 Dec, 2000 Neftali Rivera, UPR, Areci-bo, Colloquium: Arecibo Optical Astron-omy Observatory

1 Dec, 2000 Hans Moosmüller, DesertResearch Institute, University of Neva-da-Reno, Colloquium: New OpticalMethods for Monitoring AtmosphericVisibility

30 Nov, 2000 Mark Chang, UPR, Col-loquium: The Magdalena Ridge Obser-vatory - an update

21 Nov, 2000 Phil Nicholson, Cornell U.,Colloquium: The discovery of 7 newsatellites of Uranus and Saturn

6 Nov, 2000 Willem Van Driel, NançayObservatory Delphine Monnier-Ragaigne, Nançay, Colloquium: HI stud-ies of LSB galaxies at Nançay

Group shot taken during the visit by congressional staffers at the visitor center observation deck. From left:

John Harmon, Stephen Johnson, Floyd DesChamps, Karen Pearce, Ron Anderson, Chris Salter, Robert Palmer.(Photo by Tony Acevedo)

Cornell University where he is respon-sible for federal and state relations.

Comings and Goings

Hector Cruz Retires

Jonathan Friedman

Many of our readers have never metHéctor Cruz, but his absense may

well be noted. Héctor began at the Areci-bo Observatory in 1967 as a temporaryemployee doing carpentry. He was soonmoved to the full time staff in the Main-tenance Department, where he was pro-moted to Trades Foreman in 1971. In1986 he became Trades Supervisor,where he was in charge of all of thosenasty maintenance tasks that nobodywants to deal with.

In 1998, Héctor manned the local“fire tower”, stationing himself in thevicinity of the airglow and lidar labs inorder to beat back flames from a fire thatraged in the valley below. His dedica-tion and good humor will be remembered


here, and by those of our visitors whohad the honor of knowing his work atthe Arecibo Observatory.

Gersom Ortiz Leaves

Rey Vélez

Gersom Ortiz worked as an operator atthe observatory since 1998. In additionto being a diligent operator, Gersom wasa popular figure around the control roomand his artistic work was often on dis-play with spoof caricatures of variousstaff members. Gersom’s presence in thecontrol room is preserved on film due tohis “oscar-winning’’ performance in themovie: A Day in the Life of the AreciboObservatory. Gersom left the observa-tory to pursue a career in engineering;he is currently studying full time for hisMasters’ degree. We wish him all the bestand look forward to seeing him fromtime to time as a visitor to the controlroom.

New Telescope Operator: ÁngelDavíd Rodríguez

José Cruz

Ángel joined our operations group as areplacement operator for Gersom in Feb-ruary and has been rapidly learning theropes in the control room. Ángel Davídwas part of the visitor's center staff sinceits inauguration in 1997. Ángel bringsconsiderable expertise in software devel-opment to the control room and shouldbe of great help to us in a number of soft-ware-related tasks.

Adios Jean-Luc Margot

Don Campbell

After two years as a post-doctoral re-search associate at Arecibo, Jean-LucMargot has moved to sunny Californiataking up the O. K. Earl postdoctoral fel-lowship in the Division of Geologicaland Planetary Sciences at the CaliforniaInstitute of Technology. While at CaltechJean-Luc will continue working on suchtopics as radar observations of near earthobjects and studying the surface proper-ties of Venus but he has already startedusing the Keck II optical telescope tosearch for binary asteroids. He and MikeBrown of Caltech have recently an-nounced their first discovery of a mainbelt asteroid with a small companion.Jean-Luc came to Arecibo on comple-tion of his Ph.D. in the Department ofAstronomy at Cornell in early 1999.While continuing a number of studiesof the polar regions of the moon, the top-ic of his Ph.D. thesis, he immediatelybecame heavily involved in the use ofthe 13 cm radar system for asteroid stud-ies. Not content with the traditional de-lay-Doppler technique for imagingasteroids he started investigating the useof interferometry to improve the radarimages. The use of other telescopes high-lighted the need for a wide band porta-ble direct sampling system so Jean-Lucset about developing a four channel 20MHz bandwidth sampling system usingrelatively cheap PC or Sun computers.

Héctor Cruz (Photo by Tony Acevedo)

They have been used successfully at theGoldstone NASA/DSN 70m antenna, theNRAO ST Croix VLBA antenna and, ofcourse, Arecibo.

Jean-Luc’s ability, tremendous dedica-tion to his work and willingness to helpanyone who needs his assistance will besorely missed at Arecibo. We are veryhappy that he will remain connected tothe Observatory and wish him every suc-cess in his new position.

Ángel Davíd Rodríguez (Photo by Seth Shostak)

TO:

NAIC/Arecibo Observatory Newsletter504 Space Science BuildingCornell UniversityIthaca, NY 14853-6801 U.S.A.

*address correction requested

NAIC/AO Newsletter is published three times per year by theNational Astronomy and Ionosphere Center.The NAIC is operated by Cornell University under a cooperativeagreement with the National Science Foundation.

Duncan Lorimer and Jonathan Friedman, Editors

Address: NAIC/AO NewsletterHC03 Box 53995Arecibo, PR 00612

Phone: +1-787-878-2612Fax: +1-787-878-1861E-mail: [email protected] or [email protected]: http://www.naic.edu

Documents

NAIC Newsletter Number 32