3. Overview of proposal preparation, validation, submission and selection

Proposers/ guest observers will have to submit proposals to ISRO by the deadline given in the ISSDC website using AstroSat Proposal Processing System (APPS) software. APPS is available online  through http://www.issdc.gov.in.  APPS is not downloadable and cannot be used off-line. An APPS proposer’s guide will be made available in ISSDC and ASC websites which elaborates on the proposal submission procedure.  A summary is provided in this section.

3.1       Proposal preparation pre-requisites

Depending on the scientific requirement, proposals to AstroSat can be submitted for observation with a single or more instruments. Proposals are to be made as per APPS proposer’s guide and this procedures document.  Proposers can refer to redbook for the list of observed targets.

AstroSat proposals will require the following information at the minimum. 

  • Source coordinates,  source angular size if extended, V magnitude, 2-10 keV flux, estimated count rates for different instruments, exposure times, UVIT bright source list, Astroviewer output  for  feasibility of observations  of  the  target  in pdf format. (use AstroSat tools listed in section 3.3)
  • Instrument configuration parameters such as instrument mode, filter, etc. (Ref. Handbook)
  • Scientific and technical justification.

3.2       APPS Instructions

  Instructions to fill various entries within APPS to prepare proposals are available online.  APPS proposer’s guide can also be referred for this purpose.   Queries on APPS can be mailed to [email protected] / [email protected] for proposal preparation and submission.  Queries will be answered on best effort basis.

3.3       Proposal Preparation Tools

Proposers can use the following tools in order to prepare an AstroSat proposal. 

3.3.1   ASTROVIEWER - Tool to aid Celestial Source Viewing

The tool gives the view periods of a selected celestial source for a prolonged period of one year maximum.  Also, the view periods that satisfy all the constraints are provided orbit-wise so that the proposer/ Guest Observer can plan their observations more accurately and also season-wise. For UVIT payload users, view duration timings during eclipse that satisfies all envisaged constraints are available in a separate file as UVIT is expected to observe only in eclipse.  The Tool has been designed to use the latest orbit information available on a daily basis and provides the various constraint angle characteristics in graphical plots so that GO can visualize the situation while planning for observations. The view period of the selected source is stored orbit wise and is made available in tabular form for the GO to use.  Since the ram angle constraint for certain sources are on and off due to the closeness to the orbit inclination, this output contains flags ‘0’ for satisfying the constraint and ‘1’ for violating the constraint in the table.  A Graphical User Interface program allows the user to interact remotely and obtain the required details. Additional information like Eclipse and occult Entry/Exit is also made available. 

Geometrical Constraints

  • RAM angle (+ROLL and velocity vector) > 12˚
  • Terminator (+ROLL and Bright Earth Limb)  > 12˚
  • Sun Angle (+ROLL and SUN)  > 45˚ (may be  higher  depending on mission  requirement)
  • Angle b/w +YAW and SUN > 90˚
  • Angle b/w Star Sensor and SUN > 50˚  Angle b/w +ROLL and Albedo > 12˚

3.3.2       Portable Interactive Multi-Mission Simulator (PIMMS)

The AstroSat PIMMS package (downloadable from http://astrosat-ssc.iucaa.in/or accessed online at http://astrosat-ssc.iucaa.in:8080/WebPIMMS_ASTRO/index.jsp) is an implementation of the Portable Interactive Multi-Mission Simulator package, originally distributed from NASA/GSFC High Energy Astrophysics Science Archive Research Centre (HEASARC).  This implementation includes the effective area of AstroSat X-ray instruments and can be used to estimate source count rates in LAXPC, SXT, CZTI and SSM for a variety of input spectral models.  A user manual is distributed with the downloadable version, and online help is available for the WebPIMMS version.

Response files:  Response Matrix files and estimated background spectra are provided for LAXPC, SXT and CZTI payloads at the website http://astrosat-ssc.iucaa.in. These may be used to carry out spectral simulations for X-ray sources, for example with the fakeit command in HEASOFT XSPEC.

3.3.3       UVIT Exposure Time Calculator (ETC)

 Help Page: http://uvit.iiap.res.in/Software/etc/Help Present Version: 2.0.0 (03 May, 2016) The UVIT Exposure Time Calculator (ETC) will help assess the feasibility of an observation. It calculates the expected count rate from a source in various UVIT filters, followed by either i) The Signal-to-Noise Ratio (SNR) achieved for a given observation time, or ii) The time required to reach a given SNR. Users may choose from a range of astronomical sources/spectra such as a star, black-body, galaxy, power law, etc. or choose to upload their own source spectrum.

3.3.4       Bright Source Warning Tool (BSWT)  

Help Page: http://uvit.iiap.res.in/Software/bswt/Help Present Version 1.5.0 (30 March 2016) Aim of the tool is to inform the proposer whether the region of the sky around a science target is safe / unsafe for UVIT to take observations. The program scans for stars brighter than the safety threshold and lists out the count rates of these bright stars in all the 10 filters in the FUV and NUV telescopes. This program identifies all the bright stars within 20 arcmin radius of the target object.  See also guidelines document at the same website. Please note that as per the latest process used by UVIT this output is only used to check for filters of VIS (320-550 nm) channel; the checks for NUV/FUV filters are not made with this list.  Hence the following mandatory checks are necessary. 

Mandatory checks for successful observation with UVIT

The UVIT is not designed to observe very bright sources and the presence of a bright source in the UVIT field of observation can cause “Bright Object Trigger” in the hardware that would switch OFF all three detectors. In addition, the presence of an ultra-bright source near the UVIT field of view will scatter excessive radiation beyond the allowed limit. One of the UVITs, the VIS channel is primarily used for the spacecraft tracking. It is the proposers’ responsibility to ensure smooth tracking during their proposed observations. Hence the proposers need to exercise extra caution in preparing a proposal for UVIT observations. It is strongly recommended that the proposers follow the guideline described in detail in the document (ref:http://uvit.iiap.res.in/sites/uvit.iiap.res.in/files/Guidelines_for_proposal_submission_3.pdf) for mandatory checks to be done for UVIT observations.

3.4       Preparing an ASTROSAT proposal

Proposers will need to register into the APPS before they can prepare proposals.    Proposers  may  go  through  the  APPS  help  document  regarding  entry of  proposals.

There are four sections in APPS that proposers will need to complete in order to prepare a valid proposal.  AstroSat proposals must contain scientific and technical justifications and a large number of observing parameters such as the coordinates of the proposed targets, primary instrument, required total observing time, instrument configurations, etc.

Only valid submitted proposals will be reviewed. The entry of necessary observing parameters is facilitated by APPS.

There are different types of proposals like regular pointing with or without any time constraints, Monitoring proposals and anticipated ToO proposals.  Details about these may be seen in APPS proposers’ guide.

3.4.1   Cover  page

  The cover page shall contain an overview of the proposal in the form of title and abstract, the names of proposers, contact information of the Principal Investigator (PI) or Primary Observer. If a PI is a theoretician or wants to appoint a Co-Investigator (Co-I) as the primary contact person for any technical information on the proposal, the PI can assign one of the Co-Is as the primary observer.  The cover page shall also contain fields for total observing time and total stare time (any instrument overhead + total observing time). These fields will automatically be calculated from the exposure time set for the primary instrument.        

3.4.2   Target list & Instrument configurations

The target list should contain information about each proposed target such as Target name, coordinates, target angular size, variability, V magnitude and 2-10 keV X-ray flux etc.  The observing time and stare time for the target will be automatically calculated from the exposure details for the primary instrument.  Target names can be resolved with NASA Extragalactic Database (NED) or Set of Identification, Measurements and Bibliography for Astronomical Data (Simbad) and coordinates (J2000) can be fetched from these servers. Details of entering the configuration may be obtained from APPS proposer’s guide. 

3.4.3   Attachments          

The following files in pdf format ARE MANDATORY and must be attached to complete a proposal.

  •  Scientific Justification
  • Technical Justification
  • Output file from UVIT Bright source warning tool in pdf format.
  • Astroviewer output (to include view opportunity files and view opportunity in eclipse (for UVIT))

3.4.4   Supplementary Information (Optional)

            Proposers can provide supplementary information e.g., any special  requirement.

3.5       Proposal verification and submission

Proposers can validate their proposals for completeness by clicking the “Verify and Submit” tab. Note that this action does not submit the proposals; instead it highlights missing entries in various sections.  Proposers can edit different sections to complete any missing fields. The proposal submission button appears only after the verification is successful.  The proposers will be given an acknowledgment after successful submission of proposal.

  3.6       Valid proposals

 Proposals submitted in response to a call are considered valid if (i) the submission was completed as defined in this section 3.4 and (ii) the proposal is in agreement with the procedures described in this document.

Any information becoming available after the due date for proposals cannot be considered for the proposal evaluation.

By the submission of a proposal, the PI as well as all Co-Investigators are complying to the procedures described in this document.  In case of doubts about the interpretation or in case of unforeseen conflicts, the final decision lies with the ATAC.

It is the obligation of the PI to inform the APPS about every change which potentially impacts on the enhancement, the scheduling, the observation or the data distribution. Especially, the APPS should be informed about any change of the electronic address of the PI via e-mail to [email protected] / [email protected]  and writing the proposal ID number in the subject of the e-mail.

3.7       Proposal handling in APPS        

The receipt of each incoming proposal will be automatically acknowledged.   At the end of submission date, the APPS will forward them to the ATAC for scientific review, while performing some assessments and preparing overall statistics on the response.   ATAC is already constituted by Chairman, ISRO. 

The ATAC will assign priorities to each proposal as A, B and C (and, as needed, grade individual observations within a proposal). The ATAC may ask some proposers to reduce the observing time or the number of targets in a proposal. Such proposals will be made available for revision to the PIs. The proposers will be able to submit a revised proposal before the set deadline only for changes recommended by the ATAC. Such partially allocated proposals, if not revised before the deadline, will be excluded from the list of successful proposal.

The technical feasibility of making the observations will be conducted by AstroSat Technical Committee (ATC) with support from Mission operations team. 

One of the parameters used to plan which observations will be carried out during a particular orbit, is the priority of the observations as allocated by the ATAC and ATC.  However, for operational reasons, no guarantee can be given that a particular observation will in fact be executed, regardless of its grade.