AstroSat - Ground Segment
ISRO Telemetry Tracking and Command Network (ISTRAC) is bestowed with the responsibility of providing the ground support for all the phases of this mission. AstroSat Ground Segment comprises TTC (Telemetry and Telecommand) and Payload Data reception stations, Satellite Control Centre (SCC), Indian Space Science Data Centre (ISSDC) and Payload Operations Centers (POCs). AstroSat TTC & Payload Ground Station along with ISSDC is collocated in the Indian Deep Space Network Complex (IDSN), Bylalu. All these four operational areas are intimately connected through communication links. In addition to the above, there is an arrangement for the pre-processing and approval of the received request for the satellite time that streamlines the sequence of observations to be carried out considering the merit, exigency of the proposals and the constraints posed by the satellite and the geometry. These ground systems function in unison towards fulfilling the mission objectives.
TTC & Payload Data Reception Station
AstroSat Antenna (11-m) is dedicated for AstroSat TTC data &Payload data reception operations. The station is tailored to meet the mission requirements in conjunction with the onboard RF systems. A standby TTC &payload data reception station is also made available at SCC, Bangalore. For the purpose of improved visibility and extended TTC support, rest of ISTRAC S-Band Network will be utilized. The ground station transfers the TTC data to the control centre and the exclusive payload data reception stations transmit instrumentwise de-mulitplexed data to Science Data Centre, after due conditioning.
Satellite Control Centre (SCC) and Mission Operations Complex (MOX)
Satellite Control Centre comprises computers, technical facilities, Mission Control & Mission Analysis area and dedicated mission control area. At the Satellite Control Centre, the satellite health is monitored, tele-commands uplinked towards payload operations and configuration changes onboard, attitude determination, visibility generation, scheduling and archival of all TTC data sets. The timetabling for various source observations and operating various instruments is approved by a separate committee identified for this purpose. This centre houses all necessary and approved mission operation software and analysis tools. The Pre-launch simulations are also organized from this centre. ISTRAC Communication network comprising both terrestrial and satellite links, provides real time voice / data/ fax connectivity for all ground elements inclusive of launcher agency.
Payload Operations Planning
AstroSat observations are basically proposal –driven and Announcement of Opportunity comes in to effect, a year after the launch.
AstroSat Proposal Processing system (APPS) accepts all the proposals in to its proposal database and takes up further processing based on the predetermined criteria. It is also interfaced with other planning tools such as Astroviewer and Exposure Time Calculator, along with details of the instruments mode, constraints etc. The source selection and finalization shall be carried out by the AstroSat Time Allocation Committee (ATAC) assisted by the peer reviewing mechanism that assess all the proposals on their scientific merit and feasibility, and taking into account the comments of the AstroSat Technical Committee (ATC) on the proposals. The proposals cleared by ATAC will flow to ATC, which studies the feasibility of observing the sources, meeting all the spacecraft constraints. The approved proposals shall be passed on to Payload Programming System for the generation of time-lined command sequence output to be uplinked to the satellite.
ISSDC & POCs
The Indian Space Science Data Center (ISSDC) is bequeathed with the responsibility of 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. It also receives and archives the higher level products generated by POCs/Guest Observers. ISSDC also supports Scientists with Payload and instrument health monitoring facilities, in addition to serving as an alternate control centre.
Payload Operation Centres (POCs) are the instrument wise focal points. They monitor the health of the instruments, coordinates the instruments related operations, plan periodic calibrations and higher level data processing. They receive the processed data from ISSDC and return higher level products generated at POCs for archival and dissemination to general public after lock-in period.
Thus, end-to-end mission activities, involving, payload operation proposal reception & processing, command generation and uplink, payload operations, satellite orbit and attitude maintenance, payload data reception and processing, dissemination and archival activities are carried out by the unified ground segment. Above all, the ground segment is responsible for the up-keeping of this space asset that provides a conductive environment for the instrument operations, inclusive of all desired orbit and attitude.