Writing Proposals and Scheduling

Tuomas SavolainenMax-Planck-Institut f. Radioastronomie

European Radio Interferometry Summer School 2011 – Rimini, Italy

Outline• Designing an experiment– Scientific idea– Feasibility study– Choosing the array and its configuration– Some useful tools for planning

• Writing a (good) observing time proposal– Scientific justification – some dos and don’ts– Technical part– Proposal submission tools

• Schedule / observing file preparation– An example of a VLBI schedule

Designing an experiment

Designing an experiment• Begin with a scientific idea– This is the fun part, but remember that the aim must be

clear. • Make a proper literature search – has someone already

done the job?– Use ADS, CDS, NED and observatory archives– Check data from different surveys

• Make a list of targets– You may need to revise this after checking the feasibility

Which array to choose?

Select a (trial) array• Are the sources observable from the array location?

– Note the increased atmospheric noise for low-elevation sources• Continuum or spectral line?

– Which band? (Check the source velocity for line observations)– Are multiple bands needed? Simultaneously? Frequency agility

of the telescopes?– If observing lines, what is the required spectral resolution? Is

your planned setup supported by the correlator?• What is the required angular resolution?

– min/Bmax • What is the largest scale of structure?

– max/Bmin

Image courtesy of NRAO/IAU

Freq.

Angular resolution

> 1 GHz

> 100 GHz

< 1 GHz

arcmin arcsec milliarcsec

EVN

EVLAATCA

GMRT

eMERLIN

ALMA

LOFAR

VLBAPdB

Westerbork

GMVA

LBA

Evaluate feasibility

Evaluate feasibility• Need a wide field of view?– Avoid time-average

smearing -> need short correlator integration time

– Avoid bandwidth smearing -> need high spectral resolution

– Larger than the primary beam -> multiple pointings, mosaicing

– Note that this can generate a lot of data, so spend a moment thinking how you are going to handle it

Bandwidth smearing. Cotton (1999)

Evaluate feasibility• Calibration strategy

– Phase calibrators / phase-reference sources (see Bob Campbell’s talk)

– Special needs:• Astrometry • Polarimetry (antenna leagake

terms, EVPA) • Scheduling constraints

– Fixed or dynamic?– Need for dry atmosphere (at high

freq.) or quiet ionosphere (at low freq.)?

– Sun limits– Coordinated observations with

other instruments

Image courtesy of NRAO/IAU

Cas A

Does the chosen array/configuration/strategy pass? If yes, go and write a proposal. Otherwise start over.

Note about VLBI: Selecting telescopes

• Depending on the required angular resolution, sensitivity, and observing band one may choose EVN (multiple telescope choices), eVLBI, VLBA, HSA, GMVA, LBA or global VLBI

• Check the (u,v) coverage!

Examples of EVN (u,v) coverages

Archives• Check the telescope archive for earlier observations of your sources

– Need to re-observe?– Augment existing data instead starting from scratch?– Use to justify feasibility

EVN archive.jive.nl VLA, VLBA archive.nrao.edu MERLIN www.merlin.ac.uk/archive GMRT ncra.tifr.res.in/~gmrtarchive/ WSRT www.astron.nl/wsrt-archive/php/ ATCA atoa.atnf.csiro.au/

Some useful tools and links• EVN sensitivity calculator:

www.evlbi.org/cgi-bin/EVNcalc• ALMA sensitivity calculator: almascience.eso.org/call-

for-proposals/sensitivity-calculator• EVLA exposure calculator:

science.nrao.edu/facilities/evla/calibration-and-tools/exposure/evlaExpoCalc.jnlp

• ATCA observing tools: www.narrabri.atnf.csiro.au/observing/#tools

• Sched (useful for planning VLBI experiments): www.aoc.nrao.edu/~cwalker/sched/

Writing an observing proposal

Observing time proposal• Common user instruments usually announce a call for

proposals two or three times per year• ToOs are accepted any time• Different over-subscription factors at different

observatories and at different LST ranges – sometimes it pays off to know these

• A typical proposal has three parts:– Cover sheet (includes the source list and is nowadays

usually generated by a web-based proposal submission tool)

– Scientific justification– Technical justification

Scientific justification – some dos and don’ts

A good scientific justification is…•Clear and concise•Includes the necessary background material needed to understand the scientific goal – but not more•Clearly explains how the scientific goal is achieved by making the proposed observationsIt is a good idea to…•Use (clear!) figuresTry to avoid…•Unnecessary repetition•Too many buzzwords

Scientific justification – some dos and don’ts

Telescope program committees hate to see…•Poorly justified sample sizes

– Why do you want to observe 10 sources? Why not 5 or 100?•Fishing trips

– “We would like to observe this source to see if there is something interesting there.”

•“Old hats” – unnecessary repeating of old experiments•Vague claims

– No clear logical path from the observations to the astrophysical goal advertised by the proposers.

•Non-scientific (i.e. political) arguments•Proposer not adhering to the given page limit!

Technical part

• Justify the requested observing time– required rms noise– required (u,v) coverage– time needed for calibrators– Check that the required dynamic range is achievable

• If non-standard setups or a very stringent scheduling is needed, it is a good idea to consult the observatory staff beforehand – it may turn out that what you are requesting is in fact impossible to do.

Proposal submission tools• Electronic submission via web-based tools is now

the norm (an exception is for example IRAM PdB)• Different tools for different observatories– EVN, WSRT, eMERLIN: NorthStar

(proposal.jive.nl)– VLBA, EVLA: NRAO PST (my.nrao.edu)– ALMA Observing tool (download from www.almascience.org)

– ATCA (opal.atnf.csiro.au)• Usually possible to modify the proposal until DL –

Submit early, modify and re-submit!

Scheduling an observation

Scheduling• After the acceptance of the proposal:

– Preparation of the required observing files using observatory-specific tools– Observatory staff checks the observing files and schedules the observations

(either on a fixed date or dynamically)• Observing file contains:

– Array configuration– Receiver setups– Correlator setup– Scans of targets and calibrators– Constraints for dynamic scheduling– Can have a lot of details

• Pay attention to:– Visibility of the targets and calibrators – and their separation on the sky– Duty cycles– Be extra careful if using non-standard receiver setups.– Be sure to observe all the required calibrators (flux, phase, polarization

leakage and evpa, bandpass, fringe finder in VLBI observations…)

OPT for EVLA

• Log in at e2e.nrao.edu

Sched for VLBI observations• VLBI observing file (schedule) is prepared with a program called Sched,

which makes control files for all the individual telescopes (www.aoc.nrao.edu/~cwalker/sched/)

• Sched handles automatically a lot of things like calculating the slewing times of different telescopes

• Since VLBI telescopes are distributed around the world, your source transits at different times at different telescopes sites. The schedule has to match the allocated UT slot, which corresponds to the requested GST range. Use sched to check source uptimes already when planning the experiment.

• If preparing VLBI schedule for the first time, seek help from an experienced user.

• Remember to schedule strong and compact “fringe-finder” sources several times during the observation. Try to schedule these when they are observable from all the antennas.

• Send <obscode>.key file to the observatory staff

Sched for VLBI observations

Sched for VLBI observations

Future proposal deadlines• WSRT: Sep 15 2011• IRAM PdB: Sep 22 2011• EVN: Oct 1 2011• ATCA: Dec 15 2011• GMRT: Jan 15 2012• EVLA, VLBA, GMVA: Feb 1 2012• ALMA: spring 2012

GOOD LUCK WITH PROPOSAL PREPARATION!