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Announcement of Opportunity (AO) soliciting proposals for fourth AO cycle observations

AO procedures

Criteria for applying:

  • This announcement is open to Indian scientists/ researchers residing and working at institutes/Universities/colleges in India for 65% of time and to Non-Indian scientists/ researchers, Non-Resident Indians (NRIs), working at space agencies/ institutes/ Universities/ colleges around the globe for 20% time, who
  • are involved in research in the area of astronomy and
  • are equipped to submit proposals as Principal Investigators (PIs) for specific target observations with necessary scientific and technical justification and
  • can analyse the data, if the target is observed based on approvals.


1.   Introduction and Schedule

            AstroSat is the first dedicated Indian astronomy mission aimed at studying celestial sources in X-ray, UV and limited optical spectral bands simultaneously, thus providing a space astronomy observatory which is operated by the Indian Space Research Organisation (ISRO).  The satellite is at 650 km near-equatorial orbit with 6-degree orbital inclination.

AstroSat completed two years and three months in orbit.  Currently, the third AO cycle proposals are being executed.  Proposers can refer to the Redbook in the ISSDC website for the list of observed targets.

The details on the mission and payloads are available in the ISRO website.  The technical details of payloads are described in the AstroSat Handbook.

A significant amount of AstroSat’s observing time is made available to PIs of proposals, both Indian and International.  The availability of AstroSat time will be made through Announcements of Opportunity (AO).  Electronic submission of proposals through AstroSat Proposal Processing System (APPS) software at ISSDC website will be required to submit a proposal in response to this AO.  Submitted proposals will be reviewed by the AstroSat Time Allocation Committee (ATAC) and AstroSat Technical Committee (ATC) for scientific merit and technical feasibility.

The observations will be planned as per mission scheduling.  The PI will be informed, after the completion of successful observation for the downloading of processed Level-1 data.  After the 12 months proprietary period, which starts from the day Level-1 is made available to the PI, the archived data will be open to registered users and will be available in ISSDC.

This AO soliciting proposals for the fourth AO cycle is for Indian as well as international proposers as Principal Investigators (PIs) to utilise AstroSat observatory time.  The observations will be carried out in the period between October 2018 to September 2019 (approximately one year). 

 All announcements regarding exact dates and proposal submission will be from the Indian Space Science Data Centre (ISSDC) website (http://www.issdc.gov.in) and AstroSat science Support Cell (ASC) websites (http://astrosat-ssc.iucaa.in/).

For all matters related to a proposal, the Principal Investigator (PI) of the proposal is the single point of contact for ISRO.   The PI will be informed through e-mail about the status of the submitted proposals. It is expected that necessary facilities for carrying out the AO project will be provided by respective host institutions. 

The deadline for submission of proposals will be announced in ISSDC and ASC websites.

2.  Observing cycles

In this fourth AO cycle, 65% of observing time is available for Indian AO proposals and 20% of observing time is for International AO proposals.  5% time is allotted for Targets of Opportunity (ToO).  Rest of the 10% time in this cycle is allotted for collaborators and calibration.

2.1       AO cycle

AstroSat is operated in a pre-planned manner i.e proposers are not present at Mission Operations Complex during the execution of their observations.  Thus, all observations must be specified in full details in advance.

  • The percentage of observing time for executing AO proposals during October 2018 – September 2019 is 85% and is termed as fourth AO cycle.
  • Out of 85%, 65% time is exclusive for Indian proposers as Principal Investigators (PIs) to utilise AstroSat observatory time. They could be interested  researchers, scientists and astronomy community at large, involved in scientific research in the field of astronomy and are equipped to submit proposals as Principal Investigators (PIs) for specific target observations with necessary scientific and technical justification and can analyse the data, if the target is observed based on approvals. In addition, 20% of the time is for international proposers from the global astronomy community. 
  • All the selected AO proposals will be inserted into the observing schedule.  However, few observations approved in this AO cycle may be scheduled outside of the above period, in case there is operations requirement, which will be provided by AstroSat Mission.
  • Proposers are requested not to duplicate any of the planned observations and should carefully justify duplications if any, with performed observations. Proposers have to check the list of objects and instrument parameters for observations already/ being carried out using AstroSat. A Red book containing these targets will be made available in the ISSDC website. Proposers wishing to observe any of these targets should justify why it is important to do so and what additional information will come from the proposed observations. See also section 4.
  • Checks for duplications will be performed by ATAC while processing the proposals during the scientific review.

2.2       Targets of Opportunity (ToO) cycle

  • Proposals that require observation of phenomenon like outburst of a supernova or nova, observation of a new transient source or X-ray nova or study of characteristics of a source when it makes transition to a different state etc. and for which one cannot predict in advance the time of occurrence, must be submitted as ToO proposal and they will be reviewed by a separate ToO Committee.
  • A ToO cycle is always open for submitting proposals at present for any proposer. A provision of 5% observing time is reserved for ToO proposals. 
  • Data of observations made using a ToO proposal during the allotted ToO time will be made public immediately. 
  • If this time is not fully subscribed, it may be added to the time for the AO proposals.
  • Anticipated ToOs are ToOs whose source position is known but time of observation is not known or unpredictable.  The proposal for anticipated ToOs can also be submitted through APPS, which will be reviewed by ATAC committee.  The scientific justification needs to be really strong to clear the proposal and also has to get priority “A” for acceptance (refer APPS proposer's guide available in ASC website for details on anticipated ToOs and priority ranking for proposals).  However  when  the event occurs,  a  ToO  trigger  proposal  by  the PI  of  the original proposal has  to be  submitted under ToO  cycle to schedule the proposal. The data rights are same as that for AO proposals.

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

PIs of proposals  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 is 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]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 PIs of proposals 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)  > 65˚
  • 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 1.6.1 (4 July 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 to be done for UVIT observations

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, v 0.5, 09 June 2016) 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  submission of  proposals.

3.5       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.   All the committees are 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 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.  

4.   Aspects of duplication

The general policy of the ASTROSAT is to avoid repeating the same observation, i.e. to avoid duplications.

In general, a duplication is determined by consideration of the target coordinates and of the main observing parameters (especially the instrument (s) and the observing modes). A proposed observation duplicates another one, if the expected science data are essentially the same or of lower requirement (e.g. lower exposure time) and is therefore discouraged. It is, however allowed, to observe the same target with the same instrument configuration several times for variability studies.  In addition, in large extended objects several pointings in the vicinity of a source may become necessary e.g., to image Coma Cluster of galaxies out to 2 deg. diameter so as to cover its virial extent, and these may have co-ordinates that are not too different from that of the previous observation of a source.

The responsibility for defining and resolving cases of duplication rests with the ATAC . The ATAC can allow observations of same targets in a proposed observation and an observation of a previous cycle.  These should be restricted to proposals which provide convincing evidence that additional data are of scientific relevance.

5.   Data processing, data rights and publication

After the completion of observation, the raw data received will be converted to Level-1 data at Indian Space Science Data Center (ISSDC).  ISSDC is responsible for governing the ingest, Quick look Display (QLD), processing (for level-0/1), archival (all levels, along with the auxiliary data) and dissemination of payload data.   The data will be in standard FITS format.

Level-1 data can be downloaded from the ISSDC website by the payload teams or Principal Investigators (PIs) of the proposals for science analysis as well as to produce higher level data products. Sample data, software and utilities are provided in the ASC website.

The PI will be informed, after the completion of successful observation for downloading of processed Level-1 data. The standard pipeline software from Level-1 to Level-2 and any other higher level standard products will be made available to the PIs of proposals through ISSDC website.

5.1       Proprietary period                                                                                

There shall be a Proprietary period associated with observational data from all AstroSat instruments and in all phases and years after launch. This "proprietary period" would begin from the date the Level-1 data is made available to the payload teams and /or PIs of AO proposal.

During this proprietary period, the data will NOT BE USED by any persons or teams other than those who submitted the proposal(s) for the observations, except in cases where the PIs of proposals themselves involve such other persons.

The proprietary period for AO cycle data is 12 months. After the proprietary period, all data will be kept in ISSDC public archive which is accessible both nationally and internationally.  It is the responsibility of the Payload Operation Centres (POCs) to provide Level-2 products with a quality report to ISSDC.  Target of Opportunity (ToO) observations which are taken from ToO observation time will be processed immediately to Level 1 data and will be placed in ISSDC archive.  These data are non-proprietary and are open to public immediately after observation. 

 5.2      Data rights & obligations

The Principal Investigators (PIs) of all the proposals will have exclusive rights to all the data from the instruments he/ she has configured in the proposal amongst the co-aligned instruments (namely LAXPC, CZTI, SXT and twin telescope UVIT) for those fields that are observed with AstroSat against their proposals,

Data rights for other objects detected within the observed field of observation also belong to the PI of the proposal, unless they communicate not to have it.  At present there is no way to separate target data and field data.  The proposal PI may collaborate with payload teams (and vice versa) for analysis of data on field objects other than primary target.

The data rights of the instruments not configured by the PI will be made open for piggy back setting by payload teams.  Such data will be provided to the payload teams and proprietary period remains the same as AO proposal.

Any instrument team or PI has the right to reduce the proprietary period by sending an email to [email protected] with copy to ISSDC team ([email protected]) recommending for placing the data in ISSDC data archive before the end of the proprietary period. 

5.3       Publication

The proposers shall make available the salient results of the data analysis to the scientific community through publication in appropriate journals.  All the publications shall acknowledge the AstroSat data, by including a phrase “AstroSat -along with the name of the payload(s)” whose data is used for analysis/ interpretation in the abstract.

When publishing a paper using AstroSat data, please include the following acknowledgement.

“This publication uses the data from the AstroSat mission of the Indian Space Research Organisation (ISRO), archived at the Indian Space Science Data Centre (ISSDC)”.

If a user has used already published AstroSat results and carried out further interpretation or modeling, the following statement may be included in the acknowledgement.

“The research is based (partially or to a significant extent) on the results obtained from the AstroSat mission of the Indian Space Research Organisation (ISRO), archived at the Indian Space Science Data Centre (ISSDC)”.

ISRO may use any/all results that are derived from AstroSat data and published through academic papers in journals or any other publications by the user, for its own use, in its reports and publications with due reference/ acknowledgements  to such journals and publications.