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Debate: ISRO Mars Mission’s Low Science Output Still Reflects on ISRO, and Not Well

Debate: ISRO Mars Mission’s Low Science Output Still Reflects on ISRO, and Not Well

The PSLV C25 mission takes off on November 5, 2013, carrying the Mars Orbiter Mission to Earth orbit. Photo: ISRO.

This author’s article on missing science from the Indian Space Research Organisation’s (ISRO’s) Mars Orbiter Mission received a response (‘MOM’s Low Science Output Reflects Inadequate Science Base, Not on ISRO’, The Wire Science, October 1, 2020) from two planetary scientists, one of whom used to work at ISRO. The response raises some intriguing points to explain the lack of science from India’s highly regarded Mars mission, pointing to an even deeper problem. However, some points in the article that push the blame away from ISRO need to be rebutted.

The response argues that the Mars Orbiter Mission (MOM) instruments package was restricted to only 15 kg not because of the mission’s low development time of just 18 months but rather due to a technical constraint. The authors write:

“The payload was restricted to 15 kg because ISRO’s Polar Satellite Launch Vehicle (PSLV) could carry 1.4 tonnes in all to the geostationary transfer orbit. More powerful rockets – the GSLV Mk II and Mk III – with a proven track record only became available later. If ISRO had waited for these vehicles, the Mars mission would have been delayed by eight years or so.”

However, the GSLV Mk II rocket’s launch record shows that its first operational flight happened in January 2014, just two months after MOM was launched, followed by the second and third flights in 2015 and 2016. If MOM had targeted the 2016 launch window instead, it could have lifted off on an Mk II rocket, which has double the payload-carrying capacity of the PSLV.

Besides, it is not as if ISRO hasn’t carried out flagship missions on brand new rockets. The best example is the Chandrayaan 2 mission, which launched on the [GSLV Mk III’s first operational flight in 2019. So the claim that the Mars mission would have been delayed by “eight years” if ISRO had waited for these rockets does not stand – no matter how you slice the rockets’ launch history.

Next, let’s address the methane sensor, which was supposed to map methane around Mars with a sensitivity of parts per billion, to help decide if this gas could be a potential biosignature of subsurface life. Two years after launch, the instrument was found to have a design flaw, as a result of which it could not detect methane at all. The authors write:

“It did not fail; it is still working. The issue is that MSM is sensitive to both methane and carbon dioxide. And the SAC team has published a paper on a way to extract the methane signal along from the instrument’s data, subtracting the interference of other gases.”

The fact that the sensor cannot distinguish between methane and any other gas – not just carbon dioxide – and that ISRO itself officially repurposed the instrument as an albedo mapper is a failure of the original objective. The paper the authors are referring to was published in 2018; there is yet to be a single scientific publication in the two-plus years since.

Another curious case is of an instrument that this author did not address in the original article, but the authors who have responded have done so:

“Martian Exospheric Composition Explorer (MENCA) is a mass spectrometer capable of measuring parts per billion or lower concentrations of the substances in Mars’s exosphere. However, MENCA can perform its measurements only within the exosphere itself. And this hasn’t been possible thus far thanks to MOM’s orbit, which takes it to within 400 km of the surface.

Deep-dip experiments or manoeuvres are designed to make measurements closer to the lower end of Mars’s upper atmosphere. MAVEN’s lowest point was at 125 km. But MOM could deep-dive only up to 265 km – while MENCA needs to be within 100 km of the surface or less (to perform its measurements). This may become possible once MOM runs out of fuel and begins to spiral in towards the ground.”

This comment raises the question of the instrument being onboard the MOM mission in the first place. The orbit that MOM was designed for, and successfully put into, is a highly elliptical one – of 76,000 x 460 km. It hasn’t changed drastically since then, those changes being due to manoeuvres required to keep the spacecraft operational. If even during the deep-dip orbits MOM doesn’t and won’t go lower than 265 km – much higher than the less than 100 km required for MENCA – why was the instrument selected in the first place? Alternatively, why wasn’t the orbit chosen to be in line with what MENCA needs?

A spacecraft’s orbits are well known before the development of mission hardware begins. If anything, the science team usually dictates parts of these requirements. As such, the orbit chosen for MOM squarely points to the mission being a technology demonstrator instead of a scientific one.

Regarding the lack of an appropriate planetary exploration framework to drive ISRO’s space exploration missions, the authors say:

“In ISRO, the choice of what science is to be done is made by the Advisory Committee on Space Sciences (ADCOS), primarily comprising former directors of ISRO academic centres, like the Physical Research Laboratory (PRL) or the National Atmospheric Research Laboratory. ADCOS identifies experts for each proposed area of science (e.g. geology, atmospherics, etc.), with decadal plans.”

A search on ISRO’s website for more material about ADCOS returns few results, except for passing mentions that only say that ADCOS exists. This author also learnt that ADCOS has been dissolved and has been superseded by a body named APEX. But again, there is no information about APEX on ISRO’s website apart from stray mentions. The ‘decadal plans’ are nowhere to be seen. The only place displaying anything useful about APEX is ISRO’s 2019-2020 annual report. Excerpt:

“The APEX Science Board (ASB) was constituted to review and recommend steps for the cutting edge research projects on various fields related to space science. Based on the recommendations of ASB, interested scientists/faculties of various research institutes are encouraged to undertake space instrument/payload developmental activities with ISRO funding support. In addition to ongoing approved programs, feasibility studies of experiments for future space missions are also undertaken at several ISRO/[Department of Space] centres. The Apex Science Board of ISRO has selected a few scientific proposals to conduct experiments onboard an orbiter mission around Venus and Mars.”

This seems to be the only publicly available information about APEX – a bit too brief for an entire board that chooses what science will be done on ISRO’s space exploration missions. Like NASA’s decadal plans, the details of the process followed by APEX, what members are on the board and the papers that they produce should be available to the public – the taxpayers – and in an accessible way.

Regarding the criticism in the original article about ISRO not collaborating with Indian universities and institutions, the authors say:

“At ISRO’s behest, the Physical Research Laboratory initiated the Planetary Science and Exploration (PLANEX) programme in 2001. The idea was to motivate young researchers and provide planetary research facilities in the country, including for remote-sensing, astro-materials, payload development and laboratory/simulation studies of planetary analogues.

Today, a large number of projects are being run in universities and institutes around India that are supported by PLANEX. So saying ISRO isn’t as open as it can be to collaborations with academic institutions may not be entirely fair.”

Again, there is nothing on ISRO’s website or the annual report about PLANEX and its progress. Even PRL’s website is limited to a couple of sentences about the programme:

“PLANEX: Develop payloads for planetary missions, establishment of National facilities for research in planetary sciences, encourage research projects related to planetary sciences at universities and institutes in India. An X-Ray fluorescence spectrometer, electron probe micro analyser, inductively coupled plasma mass spectrometer and a noble gas mass spectrometer have been procured and are part of the national facilities for analysis of astromaterials at PRL.”

The authors end their article by pointing to the sorry state of Indian research institutions as being responsible for MOM’s missing science output, instead of ISRO. However, it is unclear why this state of affairs should spare ISRO the blame for its share of problems. ISRO is after all the one undertaking Indian planetary science missions anyway, and orchestrating related programmes.

The mystery remains as to why ISRO could not have collaborated with foreign space agencies and universities for MOM’s science, like it did with Chandrayaan 1, or taken the time to launch later with a better instruments’ package of its own.

This article was originally published on Jatan Mehta’s blog and has been republished here with permission. It has been lightly edited for style and clarity.

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