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Emily Lakdawalla • Oct 31, 2013

India prepares to take flight to Mars with the Mars Orbiter Mission (MOM)

The excitement is really building toward India's first-ever attempt at an interplanetary spacecraft! Launch day is quickly approaching for the Mars Orbiter Mission. Liftoff is still scheduled for Tuesday, November 5, 2013, at 14:38 IST (09:08 UTC / 01:08 PST). The latest news from the mission is that a launch rehearsal was successfully completed today. Isn't that rocket beautiful:

India's PSLV-C25 prepared to launch the Mars Orbiter Mission
India's PSLV-C25 prepared to launch the Mars Orbiter Mission On October 31, 2013, the Mars Orbiter Mission rested atop its Polar Satellite Launch Vehicle (PSLV) during a rehearsal of the launch, planned for November 5.Image: ISRO

After a long period of providing no official information online, ISRO has started to provide lots more information about the mission through its website and through its Facebook page, as well as a newly launched Facebook page specifically for the Mars Orbiter Mission. They've been posting lots of great photos at the mission's Facebook page, in high resolution. There is even a countdown clock. Indian websites and newspapers are bursting with articles about the mission -- I'll post a list of links to some of them at the end of the article. It's an exciting time!

Here's a graphic that shows the flight profile of the mission. The Polar Satellite Launch Vehicle (PSLV) will lift it into a highly elliptical parking orbit with a perigee of 248 kilometers and an apogee of 23,000 kilometers. Over a period of about a month, six orbital maneuvers will gradually increase the distance of the apogee. Finally, a seventh maneuver will inject the spacecraft onto a path that will transfer it to Mars. The cruise to Mars will take about ten months; it'll arrive in September or October of 2014. Its orbit at Mars will also be highly elliptical, with a periapsis of 377 kilometers and an apoapsis of 80,000 kilometers. For context, Mars' outer moon Deimos orbits at an altitude of 20,000 kilometers.

Mars Orbiter Mission trajectory infographic
Mars Orbiter Mission trajectory infographic Image: ISRO

The spacecraft carries a small payload of five instruments weighing a total of 15 kilograms. The scientific goals of the mission are rather unspecific: "Exploration of Mars surface features, morphology, mineralogy, and Martian atmosphere by indigenous scientific instrument." By "indigenous" they mean "developed in India" -- a departure from their approach with Chandrayaan-1. Science is really a secondary goal on this mission. What this mission is really about is the development of India's capability in space. The technological objectives are the main drivers. ISRO states three objectives:

  • Design and realisation of a Mars orbiter with a capability to survive and perform Earth bound manoeuvres, cruise phase of 300 days, Mars orbit insertion / capture, and on-orbit phase around Mars.
  • Deep space communication, navigation, mission planning and management.
  • Incorporate autonomous features to handle contingency situations.

Each one of these things is a tremendous challenge, and achieving any one of them will demonstrate new capability for India.

People have a lot of questions about the mission -- its capabilities, its goals, and how it fits in to the context of Mars exploration and world politics. These are all questions that I get asked a lot -- yesterday I was interviewed by Indian and British journalists and asked many of them. Here are some answers to those questions:

What is the mission's official name?
ISRO refers to it only as Mars Orbiter Mission, or MOM. It is often popularly referred to as Mangalyaan, which means "Mars-craft" in Hindi -- parallel in structure to Chandrayaan, which means "Moon-craft" -- but it's not an officially sanctioned nickname. It's popular enough, though, that people will know what you're talking about if you call it Mangalyaan. I'm sticking with the official name, Mars Orbiter Mission, but can't bring myself to call it MOM.

Why isn't it launching straight to Mars?
As originally conceived by ISRO's former chief G. Madhavan Nair, India's first Mars mission would have launched on its new, Geosynchronous Satellite Launch Vehicle (GSLV). But problems with the development of the GSLV required ISRO to make a choice between delaying the Mars Orbiter Mission and switching to the less-powerful PSLV. They opted for the latter. There is no way to launch on a direct-to-Mars trajectory with the PSLV; it simply doesn't have the power. Instead, they have to launch into Earth orbit first and slowly boost themselves into an interplanetary trajectory.

There is a silver lining to this trajectory design, though. The spacecraft can be checked out and operations begun in Earth orbit, with instantaneous, high-data-rate two-way communication. They can ease in to the more challenging deep-space phase of the mission, when the spacecraft must be able to act much more autonomously, out of range for rapid conversation with Earth.

Is the science going to be any good?
I get this question a lot. It's hard for me to assess, because I don't know very much about the instruments. It is a very, very small payload, only 15 kilograms, limited by the amount of mass they can get into Mars orbit. In fact, I learned today that the spacecraft was to have six instruments, but one instrument was dropped to keep the mass low enough. Mass serves as a useful proxy for instrument capability; lower mass usually means less capability, less precision, less reliability, etc. However, miniaturization has made great strides of late.

Ultimately, I think, this mission is really not about science. Any science returned from this mission will be a cool side benefit from a challenging, successful technological demonstration; the tech will have to succeed for the science to come.

Here is the list of instruments (descriptions copied and slightly modified from this ISRO fact sheet, with added content from this abstract presented by Jitendra Goswami and K Radhakrishnan to the 2013 Lunar and Planetary Science Conference):

  • Lyman Alpha Photometer. LAP is an absorption cell photometer. It measures the relative abundance of deuterium and hydrogen from Lyman-alpha emission in the Martian upper atmosphere (exosphere and exobase). Measurement of the deuterium to hydrogen abundance ratio allows us to understand how water is lost from the planet's atmosphere. The instrument consists of an ultraviolet detector equipped with gas-filled, pure molecular hydrogen and deuterium cells, with tungsten filaments, located between an objective lens and a detector. Here is a COSPAR presentation on LAP, which reportedly weighs only 1.5kg.
  • Methane Sensor for Mars. MSM is designed to measure methane in the Martian atmosphere with part-per-billion accuracy, and map its sources. Data is acquired only over illuminated areas, as the sensor measures reflected solar radiation. It is a Fabry-Perot Etalon sensor. [The LPSC abstract says its sensitivity to methane is at the "several ppb level."]
  • Mars Exospheric Neutral Composition Analyser. MENCA is a quadrupole mass spectrometer capable of analysing the composition of neutral species in the range of 1 to 300 atomic mass units, with unit mass resolution. [The LPSC abstract says it has 0.5 amu mass resolution.] This payload has heritage from Chandrayaan-1's Altitudinal Composition Explorer (CHACE).
  • Mars Colour Camera. MCC is a three-color camera intended to monitor dynamic events and weather on Mars. It will also be used for probing the two satellites of Mars: Phobos and Deimos. [Note: this contradicts what the MCC lead scientist, Ashutosh Arya, told me more recently.] It also provides context information for other science payloads. Its resolution will permit it to achieve instantaneous ground resolution of 25 meters and a frame size of about 50 kilometers employing a multi-element lens assembly and a 2000-pixel-square CCD.
  • Thermal Infrared Imaging Spectrometer. TIS measures thermal emission and can be operated during both day and night. Temperature and emissivity are two basic physical parameters estimated from thermal emission. TIS can map surface composition and mineralogy of Mars. TIS It uses a 120×160 element bolometer array as a detector and consists of fore-optics, slit, collimating optics, grating, and reimaging optics.

Looking at them one by one: it's hard not to compare MENCA to the Neutral Gas and Ion Mass Spectrometer (NGIMS) on MAVEN, the other spacecraft that is launching to Mars this month. NGIMS has a lower mass range (2-150 atomic mass units) but is a much larger instrument, weighing in at 27 kilograms.

The thermal imaging spectrometer sounds a bit like the Thermal Emission Spectrometer on Mars Global Surveyor, but I don't have enough information to compare them.

There has been a Lyman Alpha Photometer flown to Mars before, on the Soviet Mars 5 mission, which operated for about nine days at Mars in 1973. The National Space Science Data Center reports tersely that the "instrument performed normally and returned good data" but I couldn't find any publications about this data set; it seems this is something that the Mars Orbiter Mission could be able to improve on.

The Mars Colour Camera is intriguing. With a 2000-pixel-square three-color detector, it should be able to produce very pretty pictures of a global Mars at different phases; the phase will change over the course of the mission. I can't find very specific information about the camera's resolution, but assuming that the description of 25-meter resolution applies to its capability while at the 377-kilometer periapsis, that would mean it would have a field of view of about 7.6 degrees. That, in turn, means that all of Mars should fit comfortably within the spacecraft's field of view from distances of more than about 50,000 kilometers. If my assumptions and my calculations are correct. The orbit periapsis is 80,000 kilometers, so the spacecraft will spend quite a lot of time near this distance. If I've got my math right, then, this mission should get lots of really cool full-color global views of Mars, which would be a unique data set that would also be valuable for public outreach. I'm greatly looking forward to those photos.

Finally, there's MSM. The news from the Curiosity mission that they have been unable to detect any Martian methane, placing an upper limit of 1.4 parts per billion on its abundance in the atmosphere, has thrown a wet blanket on this investigation. However, the remote sensing work that has suggested methane's presence at Mars has suggested it's spotty and variable, so maybe it's there, just not where Curiosity is. Most scientists that I talk to seem very, very skeptical about methane on Mars at this point, but it's good that the Mars Orbiter Mission is looking for it. The most likely result from this investigation is a non-detection, which would be useful information but would not settle the question entirely; it would only place an upper limit on its abundance.

One does have to wonder how useful the data from some of these instruments, particularly the mass spectrometer, will be from the mission's very long orbit. The spacecraft will only pass close to Mars in really fast, brief sweep once every 3.2 days. Which makes one ask:

Why does it have such a long orbit?
With an orbit apoapsis of 80,000 kilometers, the Mars Orbiter Mission will be traveling very far from the planet in a very slow-moving path. This is very different from other Mars orbiters. Both Mars Odyssey and Mars Reconnaissance Orbiter are in low-altitude, circular orbits of about 300 and 400 kilometers altitude, respectively, and circle Mars in about 2 and about 1.5 hours. Mars Express is on a longer, elliptical orbit with altitude ranging from about 300 to about 10,000 kilometers and takes 7.5 hours to circle the planet.

The Mars Orbiter Mission's elliptical orbit is dictated largely by its launch vehicle. Shrinking the orbit at Mars would require more fuel, which would require more mass, and the PSLV simply can't deliver more mass onto a Mars trajectory. This orbit is the best they can achieve with the spacecraft and the launch vehicle that they have. It's not the orbit they would have chosen, had they been able to get it to a smaller orbit. ISRO's previous head is on record as saying that it is next-to-useless. I don't think I agree with that extreme opinion, but it's definitely far from ideal.

NASA has developed the capability to use aerobraking (periodic dips into the upper Martian atmosphere) to shrink their spacecraft's orbits, something that India has not attempted before. ESA is now developing their own experience at aerobraking using the Venus Express and Mars Express missions. It does seem to me that performing aerobraking experiments with the Mars Orbiter Mission would be a terrific extended mission if they are so fortunate as to have a functional spacecraft at the end of the nominal mission, but I haven't read of any plans to do this. They have to get to Mars first.

Is India in a space race with China?
I've thought a lot about this one, and I think my answer is that there's no parallel between India and China's efforts in space and the space race between the U.S. and the Soviet Union during the cold war. There is definitely competition, but the two programs really have completely different goals. For both India and China, achieving international stature is certainly one thing driving their space programs, as it is for the United States. But it's not the only goal or even the main goal.

China's program is a focused and measured one, with human exploration of the Moon as the eventual goal. Their space station program and robotic lunar exploration both represent incremental, measured steps toward that. There's no race happening because there's no one competing with them to achieve that goal. And what a proud moment it will be for China when they achieve that!

India also has international pride in mind, but to me it seems that their approach is focused more on economic development. As a rapidly developing country, it is seeking to demonstrate technological capability to the world, presenting them as a place worthy of foreign investment in high-tech industry. Getting a spacecraft into orbit at Mars is incredibly challenging. Only NASA, ESA, and the Soviet Union have ever achieved that. If they can get into orbit at Mars with a spacecraft that functions properly for more than two months, they will have bettered the Russians. So yes, India is competing with China, and Japan, and the U.S., and Europe, and so on, in an economic sense. Just the fact that India can say that is an achievement.

Discussing that inevitably brings people to the next question.

As a nation that contains hundreds of millions of people living in crushing poverty, how can they spend money on space exploration?
 This is a fair question. I've driven past slums in Mumbai with a sick feeling in my heart at the difficulty of the lives that they lead, and the enormity and complexity of the problem of improving their conditions. However, there's an error in the question. It assumes that there is a fixed quantity of wealth in India, and that stopping investment in high-tech industry would mean more money for the poor. Wealth doesn't work that way; there is not a fixed quantity of it. The technology India is developing for this mission has direct commercial applications, generating economic activity that will increase the nation's overall wealth. And I think that backers of India's space program believe that achieving a successful mission to Mars would increase confidence in India's technological prowess and therefore the flow of investment money. To be seen in the company of the U.S. and China and Europe would have to stimulate such investment.

That being said, it's true that making India overall wealthier will not necessarily benefit India's poor. Making new wealth improve the lives of India's poor depends on action by India's people and their elected representatives to accomplish that goal. The space program can't do that directly. The space program can make India wealthier.

Plus, there's a lot to be said, I think, for the intangible benefits that a nation's space program can bring to the country's mood. Even, sometimes, if it's not completely successful. I don't know India well enough to predict what will happen in the public sphere if the mission fails. Much depends on when failure happens. Blowing up on the launch pad would be heartbreaking. If they manage to depart Earth for Mars, that'll be one thing they've never achieved before, bringing them into the company of interplanetary spacefarers like the U.S., Russia, Europe, Japan, and China. If they manage to gather any data on Mars, even without entering orbit, that's another thing achieved, by only the U.S., Russia, Europe, and Japan. If they manage to enter orbit -- any orbit -- with a functioning spacecraft, that would be something that only the U.S., Russia, and Europe have managed to do. And so on.

In the event of any failure, I hope that they will consider the effort to "dare mighty things" to be its own reward. Those are words from a speech by Theodore Roosevelt. I would love to know if there is an appropriate speech on a similar theme by an Indian luminary.

It is not the critic who counts; nor the one who points out how the strong person stumbled, or where the doer of a deed could have done better. The credit belongs to the person who is actually in the arena; whose face is marred by dust and sweat and blood, who strives valiantly; who errs and comes short again and again, because there is no effort without error and shortcoming; who does actually strive to do deeds; who knows the great enthusiasms, the great devotion, spends oneself in a worthy cause; who at the best knows in the end the triumph of high achievement; and who at worst, if he or she fails, at least fails while daring greatly. Far better it is to dare mighty things, to win glorious triumphs even though checkered by failure, than to rank with those timid spirits who neither enjoy nor suffer much because they live in the gray twilight that knows neither victory nor defeat.

 Here's a list of interesting stories to read in this runup to the launch of the spacecraft.

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