Optical Telescopes.Dyer Teacher WorkshopJune, 2009 C. R. ODellVanderbilt University
Herschels Biggest Telescope
Reasons for going into SpaceEarths Atmosphere Blurs Out our View even when it is perfectly clear. This means that our view of the heavens is like that from a small telescope.Usually a bigger telescope produces a sharper image. The HST images are 20X better than what is allowed by our Atmosphere.The atmosphere also limits the energies of the photons that we can see.
1923Hermann Oberth publishes Die Rakete zu den PlanetenraumenIn this small book he elucidates most of the modern reasons for putting telescopes in space.The ability to exploit space for astronomy was and continues to be closely dependent upon transportation.
Space Travel in 1930.
1945Army Surplus V-2 Rockets come to the US.
1946The first Think-Tank, the RAND corporation commissions a study of potential uses of rockets.Lyman Spitzer, then a 32 year old professor at Yale performs this study.In this study he proposes building space observatories, leading up to something very similar to todays HST.Soon after its creation in 1958 NASA established building the HST as a long-term goal.
1971-72 NASA begins to consider the HST.One of the first things NASA did was to establish if the project was feasible (a Phase-A Study).In parallel with studies by multiple contractors a group of scientists was convened at NASA HQ by Nancy G. Roman to provide feedback.At the end of this study I was nominated by Lyman Spitzer to become the Project Scientist (September 1972).
Originally the design was for a 3-m aperture.
We had $$ problems from the beginning.The original $300M price-tag was a dictated price. Different configurations were considered.Different sizes (1.8-m, 2.4-m, 3.0-m) were considered.The 2.4-m configuration was chosen in June, 1975.ESA became a 15% partner in late 1976.
A Skeleton Sketch.
This was the first spacecraft to be designed for maintenance.
NBSAxial SI Replacement
Primary MirrorAfter Aluminizing
The telescope structure.
Focal Plane Assembly.
Transporting the Telescope to California.
OTA Development ProblemsThe manufacture of a light-weight, highly precise mirror was considered to be an established technology by the project managers.As the primary mirror was being tested and finished, the FGS was shown to be inadequate.This all occurred as a new Project Manager came on-board, whose mandate was to control the escalating costs.
Spherical AberrationThis was discovered as the first images were made.The cause was a misaligned optical device used to measure the shape of the primary mirror.This device made the mirror appear to be flat when it was of the right shape.
The Reflective Null Corrector
The Direct Mistake
Contributing FactorsThe primary mirror was not considered the most demanding part of the HST.The method of testing had become routine.Management was concentrating on a redesign of the FGS, which WAS new.The resident MSFC QA person had not been changed.The report on the anomaly with the alignment was not forwarded to MSFC.
The Assembled HST is Moved.
HST in Orbit
Servicing MissionsSM1-12/93 COSTAR, WFPC2,Solar ArraysSM2-02/97 STIS,NICMOS,FGSSM3A-12/99 FGS,Gyros,ComputerSM3B-03/02 ACS,Solar Arrays,CryoCoolerSM4-06/09 WFC3,COS,(STIS+ACS Repairs),Batteries,Gyros, etc.
The construction crane operator.
SM1Axial SI Replacement
NBSAxial SI Replacement
The Hubble Ultra Deep Field.
Who Invented the Telescope by Albert Van Helden, pp. 64-69, July, 2009 issue of Sky and Telescope.The Space Telescope by Robert W. Smith. Cambridge University Press, 1989(pre-launch) & 1993(post-launch).The Orion Nebula by C. Robert ODell, Harvard University Press, 2003 (Chapter 7).
***Oberth was a Transylvanian (an area largely filled with Germans in the mid-19th century, then connected to Romania at the dissolution of the Austro-Hungarian Empire at the end of WW-I) who did a thesis at Munich Technical University, but failed his thesis defense, but published his thesis material on the potential performance of rockets in first a short and then a long form.He then went to Berlin and became the head of a rocket society that soon was attached to the German army. A young member (18 in 1930) of this club was Wernher von Braun, who would soon eclipse his mentor.*In this circa 1930 picture Oberth stands in the middle in the long dark coat and the 18 year old von Braun is in knickers. By age 24 von Braun would have his PhD in aeronautical engineering and be the head of the German rocket program.*The V-2 rocket was developed within a German Army program to find an alternative to long-range artillery. Lead by Wernher von Braun, this highly successful rocket caused significant damage to civilian targets during WW-II. Some 200 unused ones were captured after the war and brought to White Sands, New Mexico, where there were used for various military and scientific payloads. Herb Friedman, the founder of x-ray astronomy, was one of these people in addition to Jesse Greenstein, who had a less satisfactory experience.**This study was classified for a long time, then largely unavailable, but was not forgotten by its author.*Multiple contractors were involved, being paid but a small fraction of what they spent.Members were Roman, Marc Aucremanne (engineer/manager), Aden Meinel, Bev Oke, Spitzer, Joe Wampler, me, Anne Underhill, Ernst Stuhlinger.The reps from MSFC and GSFC were essentially advocates for their institutions, with GSFC assuming they would run the HST and MSFC wanting to get the business. *From Eric Chaisson & Ray Villards April, 1990 Sky&Tel article.It is no hyperbole to say the HST is the same jump in capability as Galileos first astronomical telescope. The advantages in reaching fainter and understanding objects better that come from increased spatial resolution are manifest.Fortunately, the HST slope is slightly upward and groundbased infrared telescopes have improved and limited optical high resolution images via seeing compensation are being obtained.In the mid-70s many in Arizona were arguing against HST since active optics were just around the corner and would surpase it.Thirty years later active optics has come into wide use in the infrared, although still not producing photometrically useful images and in the optical it works, but with very serious constraints, were a little closer to that corner.*The initial GSFC configuration had a fixed set of SIs, which could be periodically serviced, possibly in a (temporary) shirtsleeves environment. *This was the 3-m configuration. The solar arrays were to fold along the telescope side, all the electronics, etc were located aft for easy servicing and the STS payload bay was filled.*Even the most honest engineers and managers can identify low costs. This is especially true when the Bankers (NASA top management) identify a low fixed number. Then it becomes a bartering situation where if you bid too low, you are likely to be buying yourself a later problem. *This is the current configuration that evolved during our Phase B studies (1973-77). It still fills the payload bay, but the solar arrays now dont increase the diameter, the goodies are packaged near the center of mass (lowering the moment of inertia and making the pointing control system easier), and the SIs are inside replaceable compartments. In order to be allowed to build the HST, an inter-agency agreement had to be made. This allowed the US to make public what its basic capability was for building telescopes in space. This also allowed the HST to utilize development procedures and numerous pieces of hardware that had already been proven. The down-side of this agreement was that the manpower at MSFC that could be assigned to the project was much lower a number than normally used for something of this magnitude. As a result, the contractors were not monitored as closely as normal. The characteristics of the HST were similar to large reconnaisance telescopes with the big difference being that HST would be inertially pointed, rather than moving rapidly to stay pointed at an object on the ground.*One of the major changes in design during Phase B was making the SIs replaceable, in order to replace failed SIs and/or replace SIs with better or different ones. Of course this also gav