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ASTROSAT
The ASTROSAT spacecraft being prepared for launch. The mission, some observers say, is another sign India is moving towards a more traditional role in space science and exploration. (credit: ISRO)

India’s space program looks outwards


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On September 28, Indian Space Research Organisation’s (ISRO) PSLV-C30 mission successfully launched seven satellites into space. This mission is significant for several reasons. First, its primary payload was a satellite called ASTROSAT, India’s first astronomy observatory to study distant celestial objects. Second, this was the 30th consecutive successful launch of ISRO’s Polar Satellite Launch Vehicle (PSLV), launching 84 satellites.

For many years, ISRO’s space program had primarily been applications oriented. Against this backdrop, ASTROSAT can be considered as India’s first mission exclusively devoted for science.

Third, there were six other co-passengers: one satellite each from Indonesia and Canada, and four nanosatellites from the US. By putting these six satellites into orbit, India has now launched 51 satellites for other countries. While there is a long history for Indo-US space collaboration, this is for the first time a US entity has used an Indian rocket to launch their satellites. Fourth, for last few years, ISRO was able to perform an average of two to three rocket launches per year. PSLV-C30 was the fourth launch undertaken by ISRO in 2015, with one to two more launches expected during the next three months. Finally, this mission featured significantly increased participation of Indian industry. According to ISRO, for this mission industry contributed almost 70 percent of the vehicle, particularly in the component arena. Also, Indian space industry was able to match ISRO’s critical schedules.

The real star of this mission, though, is ASTROSAT. This 1,513-kilogram satellite has been placed into a 650-kilometer orbit at an inclination of six degrees. This satellite will observe the universe at optical, ultraviolet, and low- and high-energy X-ray regions of the electromagnetic spectrum. This satellite is expected to have a lifetime for five years, with five instruments onboard to study various astrophysical processes. ISRO designed and developed these payloads in collaboration with various Indian agencies that do research in astrophysics. For a few payloads, the collaborative partners also include the Canadian Space Agency and University of Leicester in the UK, which assembled a sensitive CCD camera for the Soft X-ray Telescope.

According to ISRO, “the scientific objectives of ASTROSAT mission are to understand high energy processes in binary star systems containing neutron stars and black holes, to estimate magnetic fields of neutron stars and to study star birth regions and high energy processes in star systems lying beyond our galaxy. The mission is also to detect new briefly bright X-ray sources in the sky and to perform a limited deep field survey of the universe in the ultraviolet region.”

For many years, ISRO’s space program had primarily been applications oriented. ISRO began its space journey with multipurpose satellites, mainly carrying of meteorological and communications payloads. Development of Earth observation and remote sensing satellites has been a key focus of ISRO for many years. More recently, India has made significant investments in the area of space based navigation systems. The main focus of missions to Moon and Mars were technology demonstration.

Against this backdrop, ASTROSAT can be considered as India’s first mission exclusively devoted for science. This satellite is India’s first dedicated multi-wavelength space observatory proving a comprehensive understanding of the universe. The cost of building ASTROSAT is approximately US$27 million.

This astronomical satellite took far longer than expected to develop. This project started in 2004, but the scientists had a long, difficult struggle developing the various instruments for this mission.

There are many other space observatories launched long ago, like the Rossi X-ray Timing Explorer, the Chandra X-ray Observatory, XMM-Newton, Galex, FUSE, and Suzaku. These missions have mostly narrowband capabilities in either X-ray or ultraviolet regions, while ASTROSAT is a mission with broad spectral band observation capability in X-ray and ultraviolet. The focus of this mission is on high-resolution ultraviolet imaging for morphological studies of galactic and extragalactic objects, broadband studies of X-ray sources, and other multi-wavelength targets ranging from nearby stars to the very distant active galactic nuclei.

This astronomical satellite took far longer than expected to develop. This project started in 2004, but the scientists had a long, difficult struggle developing the various instruments for this mission. It took 11 years to create the soft x-ray telescope. This telescope requires 320 aluminum mirrors, which are designed and developed with great precision and given a fine gold coating. These mirrors are arranged in the form of concentric shells, with struts to hold them in place. The mirrors are positioned with an accuracy of 20 microns, which amounts to less than the width of a human hair. According to scientists involved in this project, just getting the mirrors right took about three years. This payload was jointly developed by the Tata Institute of Fundamental Research (TIFR) in Mumbai, India, and University of Leicester in the UK. The launch of this satellite was originally scheduled for 2010, but delayed until now for a number of reasons.

India launched its first satellite in 1975, called Aryabhata after an Indian astronomer of the same name. This satellite had specific scientific experiments involving X-ray astronomy and detection of high-energy neutrons and gamma rays from the sun and other objects as payloads. However, even though India’s space journey began with this science query, it did not continue with pure science experimentation. The key focus of India’s space program over the last four decades has been application-oriented programs. India made investments in the space sector essentially for socioeconomic development. ISRO launched satellites mainly for remote sensing, communication, meteorology, and navigation purposes. The only exception was its missions to Moon and Mars. However, in limited cases some Indian satellites have carried few scientific payloads too. The GSAT-2 spacecraft (launched in May 2003) carried four piggyback experimental payloads, including a radiation dose monitor and solar x-ray spectrometer. Also, a Russian-Indian scientific-educational satellite called YouthSat (launched in April 2011) had scientific payloads for observing solar flares and studying their impact on our atmosphere.

ASTROSAT is not only about astronomy. It signifies that India is now prepared to develop dedicated scientific satellite missions.

At times ISRO gets criticized for undertaking missions that have a very limited mass of scientific payloads and hence lack significant capability. For example, the scientific payload of India’s Chandrayann-1 Moon mission had a total mass of 90 kilograms and 11 instruments, while its Mars mission carried only five sensors with a combined weight of only 15 kilograms. ISRO is unable to lift heavier spacecraft because of the inherent limitations of the PSLV. But, for low Earth orbit missions like ASTROSAT, PSLV can lift much heavier payloads.

ASTROSAT is not only about astronomy. It signifies that India is now prepared to develop dedicated scientific satellite missions. Until now, India was not ready for dedicated investments into scientific missions. During the last four decades India has made significant progress in the space arena. Now, after ensuring that sufficient investments have been made towards developing space assets to satisfy social welfare needs, India appears to be ready to invest in science missions. India should no longer remain apprehensive to domestic and international criticism regarding investments in scientific research versus poverty eradication. In fact, intelligent investments in technology lead to prosperity. Ultimately, it is investments in science that could eventually lead to more technology development, and thus ISRO needs to invest even more in science missions.


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