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).

AstroSat was launched from Satish Dhawan Space Centre (SDSC), Sriharikota on 28th September 2015 by PSLV C30 (XL) to a 650 km near-equatorial orbit with 6-degree orbital inclination.   

The payloads onboard AstroSat are as follows:  The technical details of payloads are described in the AstroSat Handbook.

  • Soft X-ray Telescope (SXT) is a focusing X-ray telescope with an X-ray CCD imaging camera. This works primarily in photon counting mode, recording the position, time and energy of every detected photon in the energy range 0.3 - 8 keV.
  • Large Area X-ray Proportional Counters (LAXPC) comprising three identical proportional counters of effective area 6000 cm2 @ 5-20 keV.  This payload is non-imaging.   Its main purpose is to record variation of total intensity of sources within its 0.9 degree field of view, with high time resolution and moderate spectral resolution over a large spectral band from 3 to 80 keV.
  • Cadmium-Zinc-Telluride Imager (CZTI) is a hard X-ray coded mask camera capable of working in the band 15-100 keV.   It has a coarse imaging capability using the coded mask and can provide better spectral resolution than the LAXPC for sparse fields using weighted imaging.
  • Ultra Violet Imaging Telescope (UVIT) images the sky simultaneously in three wavelengths, the payload is configured as a pair of telescopes,  one covering the far UV band (130 – 180 nm) channel and the second covering in near UV (200 – 300nm) and visible (320 – 550 nm) channels.  The detector in each channel is a photon counting device. Multiple choices of filters are available in each channel.  The optical channel is primarily used for tracking corrections and is therefore mostly used in integration mode.
  • Scanning Sky Monitor (SSM) consists of 1D position sensitive detectors for detection of new X-ray transients and monitoring of known X-ray sources in 2.5 – 10 keV region. 

Charged Particle Monitor (CPM) an ancillary payload aimed at detecting high-energy particles (primarily protons) in the satellite orbital path and provides alerts to the other payloads, through a ground based model and / or by CPM.

The view axis of the three X-ray payloads namely LAXPC, SXT and CZTI and the UVIT are pointed along the +ve Roll direction. SSM on the other hand continuously scans the sky with its rotation axis in a perpendicular direction and monitor the intensity of X-ray sources in the field of view (FOV).


The Scanning Sky Monitor (SSM) payload and the Charge Particle Monitor (CPM) payloads are not governed by proposals.  Data updates from SSM will be provided in the Indian Space Science Data Centre (ISSDC) website after performance verification.


A significant amount of AstroSat’s observing time will be made available to proposers / guest observers (GO).  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. The availability of AstroSat time will be made through Announcements of Opportunity (AO) to submit proposals which will be reviewed for their scientific merit and technical feasibility before approval. This observing phase in which AO proposals are executed is referred as “AO cycle”.


This announcement is open to Indian scientists/ researchers residing in India and working at institutes/Universities/colleges in India, for observations from October 2016 and to international community a year later.  This first AO is exclusive for Indian proposers as Principal Investigators (PIs) to utilise AstroSat observatory time.  All announcements regarding exact dates and proposal submission will be from the Indian Space Science Data Centre (ISSDC) website (http://www.issdc.gov.in).

The first AO Cycle observations will be carried out in the period between October 2016 and March 2017 (approximately).  This AO solicits proposals for observations which can be carried out during these six months.  For next AO cycle, separate AO will be released after October 2016.


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.


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 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.


The deadline for submission of proposals is July 2016.  Exact date will be announced in ISSDC website (www.issdc.gov.in).