AstroSat

AstroSat is India's first special space telescope that can look at stars and other objects in space using many different kinds of light. It was sent into space on September 28, 2015, using a powerful rocket called PSLV-XL.

This important satellite helped scientists from ISRO study the universe in new ways. Because it worked so well, they are planning to launch a second one called AstroSat-2 to continue learning even more about space.

Overview

After the success of an earlier space experiment in 1996, India's space agency, the Indian Space Research Organisation, began planning a special astronomy satellite called AstroSat in 2004.

AstroSat carries five instruments that study different kinds of light, from visible light to special high-energy light called X-rays. This helps scientists learn about objects in space, from nearby planets to faraway stars and galaxies. The satellite was launched successfully on September 28, 2015, from India.

Mission

AstroSat is a space telescope from India designed to study many different kinds of objects in space at once. It looks at stars, galaxies, and other cosmic sources using many types of light, including visible light, ultraviolet light, and X-rays.

The telescope helps scientists watch how bright these objects change over time and study their properties. It can also discover new objects that appear suddenly in the X-ray sky. By looking at many wavelengths together, AstroSat gives a fuller picture of what is happening in space.

Payloads

The AstroSat satellite has six important tools to study space.

The Ultra Violet Imaging Telescope (UVIT) looks at ultraviolet light using three different channels. It has special mirrors and detectors to capture clear images and information about light.

The Soft X-ray imaging Telescope (SXT) uses special mirrors and a camera to study X-ray light. It can see light in the 0.3–8.0 keV range with very sharp detail.

The Large Area X-ray Proportional Counter (LAXPC) studies X-rays in the 3–80 keV range. It has three identical detectors that work together to give detailed information about X-ray sources.

The Cadmium Zinc Telluride Imager (CZTI) looks at hard X-rays from 10 to 150 keV. It uses special detectors that can see these high-energy rays very well and can also measure how the light is twisted.

The Scanning Sky Monitor (SSM) has three tools to watch the sky for X-rays. It uses a special pattern to figure out where the X-rays are coming from.

The Charged Particle Monitor (CPM) helps protect the other tools. When the satellite passes through areas with lots of charged particles, the CPM tells the satellite to turn down its power to keep the tools safe.

Ground support

The commands and control for AstroSat are handled by the ISRO Telemetry, Tracking and Command Network (ISTRAC) in Bangalore, India. During each time the satellite passes over Bangalore, scientists can send commands and receive scientific data. Out of the 14 times AstroSat orbits Earth each day, 10 of those times it can be seen from the ground station. AstroSat can collect 420 gigabits of data daily, which is downloaded during these passes using the tracking center in Bangalore. In July 2009, a third 11-meter antenna at the Indian Deep Space Network (IDSN) started operating to help track AstroSat.

AstroSat support cell

The Indian Space Research Organisation (ISRO) created a support cell for AstroSat at IUCAA in Pune. They signed an agreement in May 2016. This support cell helps scientists make proposals for using AstroSat data. It also gives them the tools, training, and help they need to work with the data.

Participants

The Astrosat project involved many different research institutions working together. Some of the main groups included the Indian Space Research Organisation, the Tata Institute of Fundamental Research in Mumbai, the Indian Institute of Astrophysics in Bangalore, and the Raman Research Institute in Bangalore. Other important groups were the Inter-University Centre for Astronomy and Astrophysics in Pune, the Physical Research Laboratory in Ahmedabad, and the Bhabha Atomic Research Centre in Mumbai. International partners included the Canadian Space Agency and the University of Leicester.

Timeline

• April 2009: Scientists from the Tata Institute of Fundamental Research finished developing the science tools for the Astrosat satellite and started putting them together. They solved problems in designing these tools and the way the satellite would point, and planned to deliver the tools to the ISRO Satellite Centre between mid-2009 and early 2010 for a launch in 2010.
• May 2015: The building of Astrosat was finished and final checks were happening. ISRO announced plans to launch it in late 2015 using PSLV C-34 to an orbit 650 km above Earth.
• 24 July 2015: Tests to prepare Astrosat for space were done. Its solar panels were attached. It began last checks to make sure it could handle shaking during launch.
• 10 August 2015: All tests were successful. A final review was completed.
• 28 September 2015: ASTROSAT was successfully launched into orbit.
• 15 April 2016: The satellite finished its checks and began its science work.
• 29 September 2018: The satellite marked three years since its launch in 2015. It had observed over 750 objects and led to nearly 100 science papers.
• 29 September 2020: The satellite finished its planned five-year mission but will keep working for many more years.
• 29 September 2025: The satellite celebrated 10 years in space. A conference was held in Bengaluru to discuss what was learned from its data.

Results

AstroSat made several important discoveries. On 5 January 2017, it detected a gamma-ray burst. This helped scientists understand that it was a different event from a gravitational wave signal detected by LIGO.

AstroSat also observed many interesting space events. It watched a small star taking material from a larger star, saw a big explosion on a star close to Earth, and captured images of faraway galaxy clusters. In 2025, researchers used AstroSat to study how a black hole’s brightness changes, which helps us learn more about black holes.

In popular culture

In 2019, a documentary called Indian Space Dreams was released. It tells the story of how the Astrosat satellite was developed, and was directed by Sue Sudbury.