India's space mission just took a giant leap with Astrosat

Flying high

  • ISRO launches Astrosat space observatory on 28 September
  • India becomes first developing nation to have a space observatory
  • Space telescope owners' club: US, Japan, Russia, Europe - and India

Looking back

  • Astrosat's mission: study the birth of stars, look for the earliest stars
  • It'll see into X-ray and ultraviolet bands for starts not visible to humans
  • And for the benefit of lay folk: take stunning pictures of the galaxies

India's stargazers finally have their own observatory in the sky. It's called Astrosat and was launched from Sriharikota, Andhra Pradesh, on the morning of 28 September.

It is India's first space observatory and the only one built in a developing nation; the others have come from the US, Japan, Russia and Europe. The most famous of the lot if the American Hubble Space Observatory, which was sent up in 1990.

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Astrosat is smaller than the Hubble - just a 10th of its size. Photo: Press Information Bureau

After settling into orbit, the observatory will weigh 1,470 kg and fly 650 km above the earth. It will take eight days to get the telescopes up and running.

But what's Astrosat and what's its mission? Catch cuts through the scientific jargon to explain why it is unlike anything India has ever sent up in space.

Clear eye in the sky

Astrosat is a space observatory, meaning it does stargazing from space. But why go all the way to space when we can observe stars from earth? Because there is a lot in the atmosphere that blocks a clear vision of the sky - light, dust, radiation. It's also why the city sky is a dark curtain, revealing just a handful of stars and planets.

Hence, the need to escape into space.

The effort is totally worth it, as the Hubble's pictures have shown. They have given us glimpses into distant galaxies, including the stunning 'Pillars of Creation', 'Mystic Mountain' and 'Veil Nebula'.

Also, the Hubble is able to see back in time. This is because light from stars far away take time to reach the telescope. So, the further you look, the older the light is and the earlier in time you're looking.

If you look up from an observatory on earth, you can see starlight from about 6 billion years after the Big Bang, but the Hubble can see light emitted just 480 million years after. In celestial terms, that is just a blink after the universe was born.

So, stargazing from space doesn't just provide dazzling images, but also deep insights into the beginning of time and the nature of our universe. Remember, we still don't know for sure how it all started!

After settling into orbit, Astrosat will weigh 1,470 kg and fly 650 km above the earth

Though Astrosat is smaller than the Hubble - just a 10th of its size - it has a wide vision. While humans can view the world only within the visible spectrum of seven colours, machines can be made to see beyond and process the view into our range of vision. In fact, many of the Hubble's famous pictures are taken this way.

Astrosat can see in ultraviolet, low and high energy X-ray band as well as the optical range visible to humans. Compared with other observatories, this is a wider range of vision, according to ISRO. This means it can look at a wider variety of celestial objects. Five different telescopes on the satellite will work together for this.

Astrosat's pictures will be merged with images taken by other observatories in space and on earth to make better, complete pictures.

Looking back in time

Most importantly, it will study the birth of stars. It's expected to look deep into the universe to see stars closer to the Big Bang, not unlike what the Hubble sees. The X-ray vision will allow Astrosat to observe star explosions while the ultraviolet vision will reveal bright stars that are far away.

In a video explaining the mission of Astrosat, ISRO summarised its significance thus: "Instead of using its vantage point in space to look down at the earth, this satellite will focus its attentions towards the heavens."

The agency says it'll be used by Indian students and scientists, who until now relied on data from foreign satellites.

The work of gathering and interpreting data from Astrosat will be shared between ISRO and astronomical institutions in the country, such as the Indian Institute of Astrophysics and the Inter University Centre for Astronomy and Astrophysics, besides other universities.

Astrosat has a wider range of vision than other observatories; it sees in ultraviolet, X-ray bands

Astrosat's launch is a rare feat for ISRO. Most of its launches are application-based, that is, they place in space satellites that are used for a specific use like telecommunications. The Astrosat, however, is purely meant to study the nature of the universe. The only other "scientific" programmes ISRO has launched so far are its well-known missions to Mars and the moon.

While the Hubble is open to amateur astronomers to gaze into space, it doesn't look like the Indian observatory will be made available for amateur use. Then again, the Astrosat will be functional for just five years; the Hubble is expected to work for at least another 15 years.

Five years though can be a long time in space observation. In its first 19 years, the Hubble's data led to a staggering 9,000 scientific papers being published.

Most of our cities might be blind to everything in the sky except Venus and the odd star, but Indian scientists are counting down to 6 October when Astrosat will open its eyes to the universe.

Nihar Gokhale

Nihar Gokhale @nihargokhale