Writing Proposals and Scheduling

1. European Radio Interferometry Summer School 2011 – Rimini, Italy Writing Proposals and Scheduling TuomasSavolainen Max-Planck-Institut f. Radioastronomie

2. 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

3. Designing an experiment

4. 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?

5. 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

6. Image courtesy of NRAO/IAU

7. Freq. ALMA GMVA > 100 GHz VLBA PdB ATCA EVLA eMERLIN > 1 GHz EVN LBA Westerbork < 1 GHz GMRT Angular resolution LOFAR arcmin arcsec milliarcsec

8. Evaluate feasibility

9. 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, sospend a moment thinking how you are going to handle it Bandwidth smearing. Cotton (1999)

10. 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 Cas A Image courtesy of NRAO/IAU Does the chosen array/configuration/strategy pass? If yes, go and write a proposal. Otherwise start over.

11. 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

12. 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 EVNarchive.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/ ATCAatoa.atnf.csiro.au/

13. 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/

14. Writing an observing proposal

15. Observing time proposal • Common user instruments usually announce a call for proposals two or three times per year • ToOsare 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

16. 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 observations It is a good idea to… • Use (clear!) figures Try to avoid… • Unnecessary repetition • Too many buzzwords

17. 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!

18. 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.

19. 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!

20. Scheduling an observation

21. 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…)

22. OPT for EVLA • Log in at e2e.nrao.edu

23. Sched for VLBI observations • VLBI observing file (schedule) is prepared with a program called Sched, which makes control filesfor 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

24. Sched for VLBI observations

25. Sched for VLBI observations

26. 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!