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Space network, a ‘hotline’ from Bangalore to moon

By Fakir Balaji, IANS,

Bangalore : When India’s first lunar spacecraft Chandrayaan-1 lifts off from Sriharikota Wednesday, the telemetry, tracking and command network (Istrac) of the space agency in Bangalore will guide the mission on its 18-day voyage to the moon’s polar orbit.

Soon after reaching the lunar orbit, the Deep Space Network (DSN) of the Indian Space Research Organisation (ISRO) at Byalalu, about 40 km from this tech hub, will take charge of the spacecraft and become a ‘hotline’ between its payloads and space scientists over the next two years.

“The ground facilities of the Chandrayaan mission comprising the spacecraft control centre (SSC) at Istrac, DSN and space science data centre (ISSDC) at Byalalu will be the channel of communication, monitoring the spacecraft’s health, including its orbit and altitude and conduct its payload operations,” Istrac director S.K. Shivakumar told IANS.

These three ground facilities will also process the wealth of data from the mission for scientists and technologists with auxiliary information. It will also be a storage centre of payload and spacecraft data.

As the focal point of the operational phase, Istrac’s s-band network stations will support the mission during the launch and early orbit phase, which includes earth transfer orbit, with an apogee of about 100,000 km.

The network’s other stations are located at Lucknow in Uttar Pradesh and at Port Louis in Mauritius. Depending on the mission requirements, network stations at Biak (Indonesia) and Bears Lake (Russia) will also be involved in the operation.

“The antennae at the network stations have been configured to support the mission during the transfer orbits, with two-carrier reception and uplink in s-band. The stations are also equipped for remote control from the network control centre,” Shivkumar explained.

The SCC will store command files forwarded from the control centre for transmission to the spacecraft as per the marked time. The tracking data comprising range, Doppler and Angle data of the spacecraft will be transferred to the control centre for orbit determination. The payload data will be transmitted to ISSDC for further processing.

“Mission activities will be conducted from SCC. The spacecraft’s health-keeping data will be monitored in real-time to ensure smooth functioning of the onboard systems.

Telecommand for change in on-board configurations and payload operations will be up-linked after verification, simulation and due authorisation. The centre will also be equipped to handle special operations and contingency recovery,” Shivakumar noted.

The DSN will transmit radio commands to the spacecraft during all the phases of the mission. It will also receive radio signals from the spacecraft, however feeble they become by the time they reach the earth.

The DSN consists of two large parabolic antennas – one with 18-metre diameter and the other with 32-metre diameter. The 32-metre antenna with its seven-mirror beam waveguide system has been indigenously designed, developed, built, installed, tested and qualified.

“The DSN with its base band system adhering to CCSDS (Consultative Committee for Space Data Systems) standards will facilitate cross-support among the telemetry tracking command agencies,” Shivakumar noted.

“The reception capability will be in both s-band and x-band. The base-band system will adhere to CCSDS standards. The station is also equipped to control remotely from the Istrac network control centre, the director said.

“All payload data in its raw form along with auxiliary spacecraft data will be received at DSN station. The data will be archived at the ISSDC, This data centre will be the repository of data from all science experiments,” Shivakumar added.

The data will be processed with software. Its dissemination will be carried out as per policy guidelines of the space agency.

Going forward, as nucleus of India’s space exploration missions, the DSN will be used for observations of celestial bodies in the solar system and for radio-astronomy observations of the universe.

For instance, the DSN provides planetary and solar scientists with data about changes in a radio signal as a spacecraft passes through a planet’s atmosphere. Scientists interpret such data to better understand planetary atmosphere.

The next mission for which DSN will be used will be Astrosat, a unique 1,000-kg space telescope designed to scout for galactic clusters, new stars beyond the Milky Way and a variety of cosmological phenomenon.