Why ASTROSAT is Not ‘India’s Hubble’

Hubble Space Telescope. Source: NASA

Hubble Space Telescope. Source: NASA

The Hubble Space Telescope needs no introduction. It’s become well known for its stunning images of nebulae and star-fields, and it wouldn’t be amiss to say the telescope has even become synonymous with images of strange beauty often from distant cosmic shores. No doubt saying something is like the Hubble Space Telescope simplifies the task of communicating that object’s potential and significance, especially in astronomy, and also places the object in stellar company and effortlessly elevates its public perception.

It’s for the latter reason that the comparison shouldn’t be made lightly. Not all telescopes are or can be like the Hubble Space Telescope, which sports some of the more cutting-edge engineering at play in modern telescopy, undoubtedly necessary to produce some of the images it produces (here’s a list of stunners). The telescope also highlighted the role of aestheticism in science: humans may be how the universe realises itself but the scope of that realisation has been expanded by the Hubble Space Telescope. At the same time, it has become so famous for its discoveries that we often pay no heed to the sophisticated physics at play in its photographic capabilities, in return for images so improbable that the photography has become irrelevant to our realisation of their truth.

ASTROSAT, on the other hand, is an orbiting telescope whose launch on September 28 will place India in the small cohort of countries that have a space-borne observatory. That’s insufficient to claim ASTROSAT will be akin to the Hubble as much as it will be India’s debut on the road toward developing “Hubble-class” telescopes. ASTROSAT’s primary science objectives are:

  • Understand high-energy processes in binary systems
  • Search for black hole sources in the galaxy
  • Measure magnetic fields of neutron stars
  • Study high-energy processes in extra-galactic systems
  • Detect new transient X-ray sources
  • Perform limited high angular-resolution deep field survey in UV

The repeated mentions of high-energy are synonymous with the parts of the electromagnetic spectrum ASTROSAT will study – X-ray and ultraviolet emissions have higher frequencies and thus higher energies. In fact, its LAXPC (Large Area X-ray Proportional Counter) instrument will be superior to the NASA NuSTAR X-ray telescope: both will be logging X-ray emissions corresponding to the 6-79 keV* energy range but LAXPC’s collecting area will be almost 10x the collecting area of NuSTAR’s. Similarly, ASTROSAT’s UV instrument, the Ultraviolet Imaging Telescope, studies wavelengths of radiation from 130 nm to 320 nm, like the Cosmic Origins Spectrograph on board the Hubble spans 115-320 nm. COS has a better angular and spectral resolution but UVIT, as well as the Scanning Sky Monitor that looks for transient X-ray sources, tops with a higher field of view. The UVIT and LAXPC double up as visible-wavelength detectors as well.

In contrast, the Hubble makes observations in the infrared, visible and UV parts of the spectrum. Its defining feature is a 2.4-m wide hyperbolic mirror that serves to ‘collect’ photons from a wide field of view onto a secondary hyperbolic mirror, which in turn focuses into the various instruments (the Ritchey-Chrétien design). ASTROSAT also has a primary collecting mirror; it is 30 cm wide.

Design of a Ritchey–Chrétien telescope. Credit: HHahn/Wikimedia Commons, CC BY-SA 3.0

Design of a Ritchey–Chrétien telescope. Credit: HHahn/Wikimedia Commons, CC BY-SA 3.0

On the road to Hubbleness

But it’s quite wrong to think ASTROSAT could be like Hubble when you consider two kinds of gaps between the instruments. The first is the technical-maturity gap. Calling ASTROSAT “India’s Hubble” will imply that ISRO has reached that level of engineering capability when it has not. And making that reference repeatedly (here, here, here and here) will only foster complacency about defining the scale and scope of future missions. One of ISRO’s principal limitations is payload mass: the PSLV rocket has been the more reliable launch vehicle at our disposal and it can lift 3,250 kg to the low-Earth orbit. The GSLV rocket can lift 5,000 kg to the low-Earth orbit (10,000 kg if an upper cryogenic stage is used) but is less reliable, although promising. So, the ASTROSAT weighs 1,500 kg while the Hubble weighs 11,110 kg – the heaviest scientific satellite launched till date.

A major consequence of having such a limitation is that the technology gets to define what satellite is launched when instead of astronomers laying out what they want to find out and technology setting out to achieve it, which could be a useful impetus for innovation. These are still early days for ISRO but it’s useful to keep in mind even this component of the Hubble’s Hubbleness. In 1974, NASA and ESA began collaborating to build the Hubble. But before it was launched in 1990, planning for the James Webb Space Telescope (JWST) – conceived from the beginning to be Hubble’s successor – began in the 1980s. In 1986, an engineer named Pierre Bely published a paper outlining how the successor will have to have a 10-m primary mirror (more than 4x the width of the Hubble’s primary mirror) and be placed in the geostationary orbit so Earth doesn’t occlude its view of space, like it does for the Hubble. But even four years later, NASA didn’t have a launch vehicle that could heft 6,500 kg (JWST’s weight) to the geostationary transfer orbit. In 2018, Europe’s Ariane 5 (ECA) will be doing the honours.

The other is the public-outreach gap. As historian Patrick McCray has repeatedly noted, telescopes are astronomers’ central research tools and the quality of astronomy research is a reflection of how good the telescopes are. This doesn’t just mean large reflecting mirrors, powerful lenses and – as it happens – heavy-lift launch vehicles but also the publication of raw data in an accessible and searchable format, regular public engagement and, most importantly, effective communication of discoveries and their significance. There was a hint of ISRO pulling off good public outreach before the Mars Orbiter Mission launched in November 2013 but that evaporated soon after. Such communication is important to secure public support, political consensus and priority funding for future missions that can expand an existing telescope’s work. For the perfect example of what a lack of public support can do, look no further than the India-based Neutrino Observatory. NASA, on the other hand, has been celebrated for its social media efforts.

And for it, NASA’s missions are more readily recognisable than ISRO’s missions, at least among people who’ve not been following ISRO’s launches closely since the 1960s. Not only that, while it was easier for NASA’s scientists to keep the JWST project from being cancelled, due to multiple cost overruns, thanks to how much its ‘predecessor’ the Hubble had redefined the images of modern astronomy since the late 1990s, the Hubble’s infamous spherical aberration fault in its first years actually delayed the approval of the JWST. McCray writes in a 2009 essay titled ‘Early Development of the Next Generation Space Telescope‘ (the name of JWST before it was changed in 2002),

Years before the Hubble Space Telescope was launched in 1990 a number of astronomers and engineers in the US and Europe were thinking hard about a possible successor to the HST as well as working to engage a broad community of researchers in the design of such a new observatory. That the launch of any such successor was likely to be many years away was also widely accepted. However, the fiasco of Hubble’s spherical aberration had a serious effect on the pace at which plans were advancing for the Next Generation Space Telescope. Thus crucially for the dynamics of building the “Next Big Machine,” the fate of the offspring was intimately tied to that of the parent. In fact, … it was only when in the mid-1990s that the NGST planning was remade by the incorporation of a series of technology developments in infrared astronomy that NASA threw its institutional weight and money behind the development of a Next Generation Space Telescope.

Autonomous shouldn’t mean opaque

But even for all the aestheticism at play, ISRO can’t be said to have launched instruments capable of transcending their technical specifications, either: most of them have been weather- and resource-monitoring probes and not crafted for the purpose of uncovering elegance as much as keeping an eye out. But that doesn’t mean, say, the technical specifications of the ASTROSAT payload shouldn’t be readily available, that there shouldn’t be one single page on which one can find all info. on ISRO missions (segregated by type: telecom, weather-monitoring, meteorology, resource-monitoring, astronomy, commercial), that there shouldn’t be a channel through which to access the raw data from its science missions**, or that ISRO continue to languish in its misguided conflation of autonomy and opacity. It enjoys a relative abundance of the former, and does not have to fight for resources in order to actualise missions it designs based on internal priorities. On the other hand, it’s also on the cusp of making a habit of celebrating frugality***, which could in principle provide the political administration with an excuse to deny increased funding in the future, and surely make for a bad idea in such an industry that mandates thoroughness to the point of redundancy as space. So, the day ought to come when the bright minds of ISRO are forced to fight and missions are chosen based on a contentious process.

There are multiple ways to claim to be the Hubble – but ASTROSAT is definitely not “India’s Hubble”. ISRO could in fact banish this impression by advertising ASTROSAT’s raw specs instead of letting people abide by inadequate metaphors: an amazing UV imager, a top-notch X-rays detector, a first class optical observer. A comparison with the Hubble also diminishes the ASTROSAT by exposing itself to be not like the Hubble at all and, next, by excluding from conversation the dozens of other space-borne observatories that it has already bested. It is more exciting to think that with ASTROSAT, ISRO is just getting started, not finished.

*LAXPC will actually be logging in the range 3-79 keV.

**There appears to be one under construction.

***How long before someone compares ASTROSAT’s Rs.178 crore to the Hubble’s $2.5 billion?

  • aj srini

    thank you for this article. recognising ISRO for their efforts should not mean indulging in jingoistic chest-thumping, hyperboles & illogical comparisons.

  • Raja2000

    You forget the Netas who will say “roll up your sleeves” to a capable organization’s leadership, an ageing organization with a mean (avg?) age of 40 years. The only thing they will understand is “India’s Hubble”.

  • Neo

    ISRO trying its best with small available funds

  • Kumar

    Can someone tell me what are the different functional satellites in the league of AstroSAT ? Hubble is one class above, but what are the major competing satellites in this league ?

    • AdRa

      Spitzer, galex are better than indian counterparts
      The rest are worse but many exist though:

      • Kumar

        coo. thanks

  • sandi

    Other not consider
    economic consideration. Look the NASA getting funding to every project but as
    compare isro work with limited budget. Also feasibility of project is also not
    consider by other. The cost at which Hubble is lunch quite high. The amount can
    be use in two mo more different kind of research. Scientific project is important but if it come with relative saving then who dont want it???

  • sandi

    Author should justified the need of TMT over Hubble.

  • sandi

    Why point is deleting??????????? Answer HUBBLE VS TMT???

  • sandi

    Hubble IN BUBBLE only.Leave it.

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  • abhishek tyagi

    Nasa. Working on moon since he sent his first man to the moon. They took a stone from THE MOON worked their butt off but could not tell the world if there exists water traces spending like trillions of dollars but in contrast INDIAN Maruti 800 sized chandrayan 1 conformed it to the world in just 8 months. Although it was a failure lol. Similarly nasa working on Mars sending rovers but could not confirm that it may have the presence of methane. I remember saying one personality that nasa says there is no methane on the Mars then why the hell they keep on sending the rovers. ISRO chairman on the occasion said nasa may be wrong and that is the fact now MOM says that life is possible on Mars. I don’t understand there are approx 30% Indians working and in ISRO 98% so how could it possibly be more smarter than ISRO . nasa is wasting their money but ISRO she is beautiful. Why is it that nasa today used India’s PSLV for the launch of its mini satellites. All I know is ISRO has taken the command of the space exploration and it will now lead the scientific community in the right direction rather than saying there is nothing out there. Poor NASA.

    thanking you.

  • So Nyuh Shi Dae

    I didn’t think one would have to write such a scientifically explained article on why we cannot compare Astrosat with Hubble. It was pretty much straighforward that India doesn’t have the capability yet, but it is still India’s hubble as in India’s first space observatory.

  • Sunil S

    According to the latest brochure of ISRO, the UVIT operates in the wavelength range: 130-650 nm, clearly including the optical region of the electromagnetic spectrum!
    I would say that nothing is wrong in calling the mission at least as ‘India’s mini-hubble mission’! And as you mentioned, in some of its characteristics, it is even superior to some other NASA instruments! And also consider the range of ‘colors’ through which it can look at the Universe!

  • ani1993

    Why can’t you just appreciate ISRO’s efforts for once instead of always taking a skeptical view?

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  • Rahul

    AstroSAT is not Hubble, there is no doubt, But why is it irritating if someone calls it so?

    If I call Stephen Hawking as today’s Albert Einstein, would you write an article to point out that he is not?

    What if someone says that his baby has twinkling eyes like stars? would you take out your charts to prove that there is a difference between star and eyes?

  • PRex

    The article only lays bare the author’s intent to prevent Indians from feeling too proud of ISRO’s achievement. “Take them down a few notches” is what I can see him saying. Otherwise this article serves no purpose at all. Any fool can see that calling Astrosat “India’s Hubble” is merely the use of a conceptual metaphor to explain it’s purpose in a very broad sense. Not worth ranting about.

  • shobhit bansal

    India’s hubble doesn’t mean India’s answer to Hubble.