Awk CZTI result from Crab pulsar

An instrument onboard the ISRO Astrosat space-telescope has studied how X-rays being emitted by the Crab pulsar are being polarised, and how such polarisation varies from one pulse to the next. This is very important information for understanding how pulsars create and emit high-energy radiation – information that we haven’t been able to obtain from any other pulsars in the known universe. The underpinning study was published in Nature Astronomy on November 6, 2017.

Quick recap: CZTI stands for the Cadmium Zinc Telluride Imager, a 16-MP X-ray camera and, as The Wire has discussed before, one of the best in its class – in the league of the NASA Fermi and Swift detectors and even better in the 80-250 keV range. Pulsars are rotating neutron stars that emit focused beams of high-energy radiation from two polar locations on their surface. (As it rotates, the beams sweep past Earth like a lighthouse sweeping past ships, giving the impression that it’s blinking, or pulsating). We study them because they’re extreme environments that can help validate theories by pushing them to their limits.

There are two things notable about the current study: how CZTI studied the pulsar and what it found as a result.

1. How – The Crab pulsar, the remnant of a star that went supernova in 1,058 AD, is located 6,500 lightyears away in the direction of the Taurus constellation. Second, pulsars – despite their remarkable radiation output – emit few X-ray photons that can be studied from near Earth. Third, the Crab pulsar has a rotation period of 33 ms (i.e. very fast). For these reasons, CZTI couldn’t just study the pulsar directly and hope to find what it eventually did. Whatever X-ray was collected would’ve had to be precisely calibrated in time. So the CZTI team* partnered up with the Giant Metrewave Radio Telescope in Pune and the Ooty Radio Telescope in Muthorai (Tamil Nadu) for the ephemeris data. In all, there were 21 observations made over (CZTI’s first) 18 months.

2. What – Like a Ferrero Rocher from hell, a pulsar is a rotating neutron star on the inside, wrapped in a very strong magnetic field. Astronomers think charged particles are accelerated by this field and the energy they emit is shot into space, as X-rays + other frequencies of radiation. So studying how these X-rays are polarised could provide more info on how a pulsar produces its famous sweeping pulses. The CZTI data had a surprise: hard X-rays are being emitted by the Crab pulsar in the off-pulse – or the-beam-is-not-pointing-at-us – phase. In other words, the magnetic field isn’t involved in producing these X-rays; the neutron star itself is. Dun dun duuuuuuun!

It’s always nice to get science results that send researchers back to the proverbial drawing board, like the CZTI result has. It’s sweeter still when local researchers are involved – and even sweeter to be reminded that we haven’t been entirely left behind in non-theoretical particle physics research. There’s even more X-ray astronomy in India’s future. After Astrosat, launched in September 2015, ISRO has okayed a proposal from the Raman Research Institute (RRI), Bengaluru, to build an X-ray polarimeter instrument that the org will launch in the future (date not known). Called Polix, it is similar to the NASA GEMS probe that stalled in 2012.

*The CZTI team had scientists from Physical Research Laboratory, Ahmedabad; Tata Institute of Fundamental Research, Mumbai; Inter-University Centre for Astronomy and Astrophysics, Pune; IIT Powai; National Centre for Radio Astronomy, Pune; Vikram Sarabhai Space Centre, Thiruvananthapuram; ISRO, Bengaluru; and RRI.

Featured image: A composite image of the Crab Nebula showing the X-ray (blue), and optical (red) images superimposed. The size of the X-ray image is smaller because the higher energy X-ray emitting electrons radiate away their energy more quickly than the lower energy optically emitting electrons as they move. Caption and credit: NASA/ESA.

The Wire
November 7, 2017

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No Space Age for us

There’s a 500-word section on the Wikipedia page for the NASA Space Shuttle that describes the markings on the programme’s iconic orbiter vehicle (OV). Specifically, it talks about where the words ‘NASA’ and ‘USA’ appeared on the vehicle’s body, if there were any other markings, as well as some modifications to how the flag was positioned. Small-time trivia-hunters like myself love this sort of thing because, whether in my imagination or writing, being able to recall and describe these markings provides a strong sense of character to the OV, apart from making it more memorable to my readers as well as myself.

These are the symbols in our memories, the emblem of choices that weren’t dictated by engineering requirements but by human wants, ambitions. And it’s important to remember that these signatures exist and even more so to remember them because of what they signify: ownership, belonging, identity.

Then again, the markings on an OV are a part of its visual identity. A majority of humans have not seen the OV take off and land, and there are many of us who can’t remember what that looked like on TV either. For us, the visual identity and its attendant shapes and colours may not be very cathartic – but we are also among those who have consumed information of these fascinating, awe-inspiring vehicles through news articles, podcasts, archival footage, etc., on the internet. There are feelings attached to some vague recollections of a name; we recall feats as well as some kind of character, as if the name belonged to a human. We remember where we were, what we were doing when the first flights of iconic missions took off. We use the triggers of our nostalgia to personalise our histories. Using some symbol or other, we forge a connection and make it ours.

This ourness is precisely what is lost, rather effectively diluted, through the use of bad metaphors, through ignorance and through silence. Great technology and great communication strive in opposite directions: the former is responsible, though in only an insentient and mechanistic way, for underscoring the distance – technological as much as physical – between starlight and the human eye that recognises it; the latter hopes to make us forget that distance. And in the absence of communication, our knowledge becomes clogged with noise and the facile beauty of our machines; without our symbols, we don’t see the imprints of humanity in the night sky but only our loneliness.

Such considerations are far removed from our daily lives. We don’t stop (okay, maybe Dennis Overbye does) to think about what our journalism needs to demand from history-making institutions – such as the Indian Space Research Organisation (ISRO) – apart from the precise details of those important moments. We don’t question the foundations of their glories as much as enquire after the glories themselves. We don’t engender the creation of sanctions against long-term equitable and sustainable growth. We thump our chests when probes are navigated to Mars on a Hollywood budget but we’re not outraged when only one scientific result has come of it. We are gratuitous with our praise even when all we’re processing are second-handed tidbits. We are proud of ISRO’s being removed from bureaucratic interference and, somehow, we are okay with ISRO giving access only to those journalists who have endeared themselves by reproducing press releases for two decades.

There’s no legislation that even says all knowledge generated by ISRO lies in the public domain. Irrespective of it being unlikely that ISRO will pursue legal action against me, I do deserve the right to use ISRO’s findings unto my private ends without anxiety. I’m reminded every once in a while that I, or one of my colleagues, could get into trouble for reusing images of the IRNSS launches from isro.gov.in in a didactic video we made at The Wire (or even the image at the top of this piece). At the same time, many of us are proponents of the open access, open science and open knowledge movements.

We remember the multiwavelength astronomy satellite launched in September 2015 as “India’s Hubble” – which only serves to remind us how much smaller the ASTROSAT is than its American counterpart. How many of you know that one of the ASTROSAT instruments is one of the world’s best at studying gamma-ray bursts? We discover, like hungry dogs, ISRO’s first tests of a proto-RLV as “India’s space shuttle”; when, and if, we do have the RLV in 2030, wouldn’t we be thrilled to know that there is something wonderful about it not just of national provenance but of Indian provenance, too?

Instead, what we are beginning to see is that India – with its strapped-on space programme – is emulating its predecessors, reliving jubilations from a previous age. We see that there is no more of an Indianess in them as much as there is an HDR recap of American and Soviet aspirations. Without communication, without the symbols of its progress being bandied about, without pride (and just a little bit of arrogance thrown in), it is becoming increasingly harder through the decades for us – as journalists or otherwise – to lay claim to something, a scrap of paper, a scrap of attitude, that will make a part of the Space Age feel like our own.

At some point, I fear we will miss the starlight for the distance in between.

Update: We are more concerned for our machines than for our dreams. Hardly anyone is helping put together the bigger picture; hardly anyone is taking control of what we will remember, leaving us to pick up on piecemeal details, to piece together a fragmented, disjointed memory of what ISRO used to be. There is no freedom in making up your version of a moment in history. There needs to be more information; there need to be souvenirs and memorabilia; and the onus of making them needs to be not on the consumers of this culture but the producers.

‘World class’ optical telescope – India’s largest – to be activated near Nainital

Update: This article was written before the telescope was activated yesterday. Here’s the PIB announcement.

India’s largest ground-based optical telescope, in Devasthal in Uttarakhand, is set to be switched on on March 30 by the Prime Ministers of India and Belgium from Brussels, during Narendra Modi’s day-long visit to the country. The telescope is the product of an Indo-Belgian collaboration, assisted by the Russian Academy of Sciences, that was kicked off in 2007. It is going to be operated by the Aryabhatta Research Institute of Observational Sciences (ARIES), an autonomous research body under the Department of Science and Technology.

The instrument is part of a widening foray into observational research in astronomy that India has undertaken since the 1960s, and bolstered with the successful launch of its first multi-wavelength satellite (ASTROSAT) in September 2015. And apart from the merits it will accord Indian astronomy, the Devasthal optical telescope will also be Asia’s largest ground-based optical telescope, succeeding the Vainu Bappu Observatory in Kavalur, Tamil Nadu.

A scan of the sketch of the 3.6-m optical telescope. Credit: ARIES

A scan of the sketch of the 3.6-m optical telescope. Credit: ARIES

Its defining feature will be a 3.6-metre-wide primary mirror, which will collect light from its field of view and focus it onto a 0.9-m secondary mirror, which in turn will divert it into various detectors for analysis. This arrangement, called the Ritchey-Chrétien design, is also what ASTROSAT employs – but with a 30-cm-wide primary mirror. In fact, by contrast, the mirrors and six instruments of ASTROSAT all weigh 1,500 kg while the Devasthal telescope’s primary mirror alone weighs 4,000 kg.

A better comparison would be the Hubble space telescope. It manages to capture the stunning cosmic panoramas it does with a primary mirror that’s 2.4 m wide. However, Hubble’s clarity is much better because it is situated in space, where Earth’s atmosphere can’t interfere with what it sees.

Nonetheless, the Devasthal telescope is located in a relatively advantageous position for itself – atop a peak 2.5 km high, 50 km west of Nainital. A policy review published in June 2007 notes that the location was chosen following “extensive surveys in the central Himalayas” from 1980 to 2001. These surveys check for local temperature and humidity variations, the amount of atmospheric blurring and the availability of dark nights (meeting some rigorous conditions) for observations. As the author of the paper writes, “The site … has a unique advantage of the geographical location conducive for astronomical observations of those optical transient and variable sources which require 24 h continuous observations and can not be observed from [the] east, in Australia, or [the] west, in La Palma, due to day light.”

From this perch, the telescope will be able to log the physical and chemical properties of stars and star clusters; high-energy radiation emanating from sources like blackholes; and the formation and properties of exoplanets. The data will be analysed using three attendant detectors:

  • High-resolution Spectrograph, developed by the Indian Institute of Astrophysics, Bengaluru
  • Near Infrared Imaging Camera, developed by the Tata Institute of Fundamental Research, Mumbai
  • Low-resolution Spectroscopic Camera

“India has collaborated with a Belgian company called AMOS to produce this [telescope], which is the first of its kind in the whole of Asia,” said Vikas Swarup, spokesperson of the Ministry of External Affairs, in a statement. AMOS, an acronym for Advanced Mechanical and Optical Systems, was contracted in 2007 to build and install the mirrors.

When Modi and Michel complete the so-called ‘technical activation’ to turn the Devasthal instrument on, it will join a cluster of scopes at the Indian astronomical research community’s disposal to continue surveying the skies. Some of these other scopes are the Giant Metre-wave Radio Telescope, Pune; Multi Application Solar Telescope, Udaipur; MACE gamma-ray telescope, Hanle; Indian Astronomical Observatory, Leh; Pachmarhi Array of Cherenkov Telescopes, Pachmarhi; and the Ooty Radio Telescope, Udhagamandalam.

In fact, over the last few years, the Indian research community has positioned itself as an active player in international Big Astronomy. In 2009, it pitched to host a third advanced gravitational-waves observatory, following the installation of two in the US, and received governmental approval for it in February 2016. Second: in December 2014, India decided to become a full partner with the Thirty Meter Telescope (TMT) collaboration, a bid to construct an optical telescope with a primary mirror 30 metres wide. After facing resistance from the people living around the venerated mountain Mauna Kea, in Hawaii, atop which it was set to be built, there are talks of setting it up in Hanle. Third: in January 2015, the central government gave the go-ahead to build a neutrino observatory (INO) in Theni, Tamil Nadu. This project has since stalled for want of various state-level environmental clearances.

All three projects are at the cutting edge of modern astronomy, incorporating techniques that have originated in this decade, techniques that take a marked break from the conventions in use since the days of Galileo. That Modi has okayed the gravitational waves observatory is worth celebrating – but the choices various officials will make concerning the INO and the TMT are still far from clear.

The Wire
March 30, 2016

Ways of seeing

A lot of the physics of 2015 was about how the ways in which we study the natural world had been improved or were improving.

Why this ASTROSAT instrument could be a game-changer for high-energy astrophysics

On November 17, NASA announced its Swift satellite had recorded its thousandth gamma-ray burst (GRB), an important milestone that indicates how many of these high-energy explosions, sometimes followed by the creation of blackholes, happen in the observable universe and in what ways.

Some five weeks before the announcement, Swift had observed a less symbolically significant GRB called 151006A. Its physical characteristics as logged and analysed by the satellite were quickly available, too, on a University of Leicester webpage.

On the same day as this observation, on October 6, the 50-kg CZTI instrument onboard India’s ASTROSAT space-borne satellite had come online. Like Swift, CZTI is tuned to observe and study high-energy phenomena like GRBs. And like every instrument that has just opened its eyes to the cosmos, ISRO’s scientists were eager to do something with it to check if it worked according to expectations. The Swift-spotted GRB 151006A provided just the opportunity.

CZTI stands for Cadmium-Zinc-Telluride Imager – a compound of these three metals (the third is tellurium) being a known industrial radiation detector. And nothing releases radiation as explosively as a GRB, which have been known to outshine the light of whole galaxies in the few seconds that they last. The ISRO scientists pointed the CZTI at 151006A and recorded observations that they’d later compare against Swift records and see if they matched up. A good match would be validation and a definite sign that the CZTI was working normally.

It was working normally, and how.

NASA has two satellites adept at measuring high-energy radiation coming from different sources in the observable universe – Swift and the Fermi Gamma-ray Space Telescope (FGST). Swift is good at detecting incoming particles that have an energy of up to 150 keV, but not so good at determining the peak energy of hard-spectrum emissions. In astrophysics, spectral hardness is defined as the position of the peak – in power emitted per decade in energy – in the emission spectrum of the GRB. This spectrum is essentially a histogram of the number of particles with some values of a property that strike a detector, so a hard-spectrum emission has a well-defined peak in that histogram. An example:

The plot of argon dense plasma emission is a type of histogram – where the intensity of photons is binned according to the energies at which they were observed. Credit: Wikimedia Commons

The plot of argon dense plasma emission is a type of histogram – where the intensity of photons is binned according to the energies at which they were observed. Credit: Wikimedia Commons

FGST, on the other hand, is better equipped to detect emissions higher than 150 keV but not so much at quickly figuring out where in the sky the emissions are coming from. The quickness is important because GRBs typically last for a few seconds, while a subcategory of them lasts for a few thousandths of a second, and then fade into a much duller afterglow of X-rays and other lower-energy emissions. So it’s important to find where in the sky GRBs could be when the brighter flash occurs so that other telescopes around the world can better home in on the afterglow.

This blindspot between Swift and FGST is easily bridged by CZTI, according to ISRO. In fact, per a deceptively innocuous calibration notice put out by the organisation on October 17, CZTI boasts the “best spectral [capabilities] ever” for GRB studies in the 80-250 keV range. This means it can provide better spectral studies of long GRBs (which are usually soft) and better localisation for short, harder GRBs. And together, they make up a strong suite of simultaneous spectral and timing observations of high-energy phenomena for the ASTROSAT.

There’s more.

Enter Compton scattering

The X-rays and gamma rays emanating from a GRB are simply photons that have a very low wavelength (or, very high frequency). Apart from these characteristics, they also have a property called polarisation, which describes the plane along which the electromagnetic waves of the radiation are vibrating. Polarisation is very important when studying directions along long distances in the universe and how the alignment of intervening matter affects the path of the radiation.

All these properties can be visualised according to the wave nature of radiation.

But in 1922, the British physicist Arthur Compton found that when high-frequency X-rays collided with free electrons, their frequency dropped by a bit (because some energy was transferred to the electrons). This discovery – celebrated for proving that electromagnetic radiation could behave like particles – also yielded an equation that let physicists calculate the angle at which the radiation was scattered off based on the change in its frequency. As a result, instruments sensitive to Compton scattering are also able to measure polarisation.

Observed count profile of Compton events during GRB 151006A. Source: IUCAA

Observed count profile of Compton events during GRB 151006A. Source: IUCAA

This plot shows the number of Compton scattering events logged by CZTI based on observing GRB 151006A; zero-time is the time at which the GRB triggered the attention of Swift. That CZTI was able to generate this plot was evidence that it could make simultaneous observations of timing, spectra and polarisation of high-energy events (especially in X-rays, up to 250 keV), lessening the burden on ISRO to depend on multiple satellites for different observations at different energies.

The ISRO note did clarify that no polarisation measurement was made in this case because about 500 Compton events were logged against the 2,000 needed for the calculation.

But that a GRB had been observed and studied by CZTI was broadcast on the Gamma-ray Coordinates Network:

V. Bhalerao (IUCAA), D. Bhattacharya (IUCAA), A.R. Rao (TIFR), S. Vadawale (PRL) report on behalf of the Astronaut CZTI collaboration:

Analysis of Astronaut commissioning data showed the presence of GRB 151006A (Kocevski et al. 2015, GCN 18398) in the Cadmium Zinc Telluride Imager. The source was located 60.7 degrees away from the pointing direction and was detected at energies above 60 keV. Modelling the profile as a fast rise and exponential decay, we measure T90 of 65s, 775s and 50s in 60-80 keV, 80-100 keV and 100-250 keV bands respectively.

In addition, the GRB is clearly detected in a light curve created from double events satisfying Compton scattering criteria (Vadawale et al, 2015, A&A, 578, 73). This demonstrates the feasibility of measuring polarisation for brighter GRBs with CZTI.

That CZTI is a top-notch instrument doesn’t come as a big surprise: most of ASTROSAT’s instruments boast unique capabilities and in some contexts are the best on Earth in space. For example, the LAXPC (Large Area X-ray Proportional Counter) instrument as well as NASA’s uniquely designed NuSTAR space telescope both log radiation in the 6-79 keV range coming from around blackholes. While NuSTAR’s spectral abilities are superior, LAXPC’s radiation-collecting area is 10x as much.

On October 7-8, ISRO also used CZTI to observe the famous Cygnus X-1 X-ray source (believed to be a blackhole) in the constellation Cygnus. The observation was made coincidental to NuSTAR’s study of the same object in the same period, allowing ISRO to calibrate CZTI’s functioning in the 0-80 (approx.) keV range and signalling the readiness of four of the six instruments onboard ASTROSAT.

The two remaining instruments: the Ultraviolet Imaging Telescope will switch on on December 10 and the Soft X-ray Telescope, on December 13. And from late December to September 2016, ISRO will use the satellite to make a series of observations before it becomes available to third-parties, and finally to foreign teams in 2018.

The Wire
November 21, 2015

Space is necessarily multifarious, ISRO

Here’s a great example of why space-exploration is a multifarious industry where it takes excellence on multiple fronts at the same time to make each mission a success, even on seemingly unrelated fronts. The example also shows the pride of financial frugality can last only for so long.

Despite many firsts, ISRO mum on MOM’s findings – Times of India

Answering a specific question after the launch of Astrosat, India’s first astronomy satellite, on September 28, Isro chairman AS Kiran Kumar told TOI: “I cannot get into the specifics. I can, however, say there are several firsts that MOM has found. But it is only fair that the principal investigators (scientists who made the payloads) claim it first in scientific journals.”

Isro was to make this data public on September 24, MOM’s first anniversary in the Martian orbit. The agency, however, had a low-key event on the day and did not reveal anything.

Equipping instruments to be able to capture and relay 1 TB of data a year is only half the job done, the other being to be able to process and publicise it. And without the need to innovate rapidly nor clamour for public support, I don’t think ISRO will ever reform this slow-moving attitude. This is NASA really cashing in – there’s no reason ISRO should be able to, too. Later in the same piece,

So between September 24, 2014 and September 24, 2015, when MOM completed one year in the Martian orbit, it could have taken 456 pictures, of which Isro has made public 13 pictures, with some repetitions of the same spot on Mars.

The pitfalls of thinking that ASTROSAT will be ‘India’s Hubble’

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

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.

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?

ISRO to launch India’s first astronomy satellite on September 28

India’s first astronomy satellite will be launched on September 28. ISRO has noted that while it has launched payloads capable of making astronomical observations before, this is the first time one dedicated to astronomy will be launched. Called ASTROSAT, it was first scheduled for launch in 2005, then in 2010, and finally in 2015 with delays largely due to putting the scientific payload together. ASTROSAT will be a multi-wavelength mission, observing the cosmos in X-ray, visible and UV light.

ASTROSAT is one of two scientific missions that have long been overdue – the other being the Aditya-1 mission to study the Sun. ASTROSAT comprises five scientific instruments, all of which had been delivered to the ISRO Satellite Centre by 2014. They are the UV Imaging Telescope, the Scanning Sky Monitor, the Cadmium-Zinc-Telluride Imager, the Soft X-ray Telescope and three identical Large Area Xenon Proportional Counters. The Soft X-ray Telescope reportedly took 11 years to be built.

X-ray and UV radiation fall in the short-wavelength part of the electromagnetic spectrum, and their emissions in the universe can’t be detected at ground level because the high-energy photons that constitute the radiation can’t easily penetrate Earth’s atmosphere. The opposite is true for long-wavelength radiation like radio waves. As a result, the most powerful and effective X-ray and gamma-ray satellites are in Earth-orbit whereas radio-telescopes – with their giant telltale antenna dishes – are on ground.

Transmission properties of radiation of different wavelengths. Source: Caltech

Transmission properties of radiation of different wavelengths. Source: Caltech

One of the better known examples of multi-wavelength space-borne observatories is the Hubble Space Telescope, which makes observations in the UV, visible and infrared parts of the spectrum. However, comparisons between the telescopes are unfounded because Hubble’s optical mirror is eight-times as wide as ASTROSAT’s, allowing for a deeper field of view and much better imaging. Nonetheless, ASTROSAT will be able to contribute in the study of time-variable sources of radiation by being able to observe the sources in UV and X-ray wavelengths simultaneously.

Eleven years after the project was first okayed, the satellite is slated to be launched on board a PSLV rocket on its 30th flight from the Satish Dhawan Space Centre at Sriharikota on September 28. Four smaller American, one Indonesian and one Canadian satellites will also be launched as part of the same mission. ISRO has stated that open observing time will be available on the satellite’s instruments from September 2016, from their perch in the near-Earth orbit at an altitude of 650 km. ASTROSAT cost Rs.178 crore.