The Indian Mars Orbiter Mission (MOM)
The latest orbiter to reach Mars was launched by the Indian government. The Indians are the latest member in a most exclusive club to reach the red planet, which includes Russia, Europe and the USA. Interestingly, they are the first nation to successfully reach Mars orbit on their first attempt. The MOM (Mars Orbiter Mission) was conceived, designed, and manufactured in India, using locally designed parts and labour. It is also called by the name Mangalyaan "Mars-craft", which in Sanskrit is मंगल (maṅgala or "Mars") and यान (yāna "vehicle").
Wednesday, September 24th, 2014 was the Big Day for the ISRO (Indian Space Research Organisation) as this ambitious mission came to fruition. After a journey of 680 million kilometers, MOM autonomously performed its orbital insertion burn to kill off its speed so it could be captured by Mars’ gravitational field. The onboard system ended the burn early when the correct delta-V (change in velocity) was achieved early due to the efficiency of the engines. Total burn time was a shade over 23 minutes using up most of its remaining fuel, as planned (approximately 250 kilograms/550 lbs) leaving about 40 kilograms (88 lbs) for orbital maneuvering during its mission.
The inclination of the orbit is at the projected 150 degrees with a periapsis (closest point to Mars) of 421 kilometers (261 miles) and an apoapsis (furthest point from Mars) of 77,000 km (47,800 miles), considerably closer than the nominal 80,000 km (49,700 miles), which should be a significant advantage for the science team.
Challenges right from the Beginning
Initially planned to launch aboard the GSLV (GeoSynchronous Launch Vehicle), there was a “last minute” change to the PSLV (Polar Satellite Launch Vehicle) because there were unresolved difficulties with the GSLV, which had failed on two previous occasions. The PSLV, a considerably less powerful rocket, was used in the PSLV-XL variation, going from nine tons of propellant to twelve.
Plans optimistically hoped that the GSLV’s problems would have been solved, and they built MOM with more weight and capabilities; but when it became clear that the GSLV wasn’t going to be available, they slimmed down the MOM and went to the back-up plan. The alternative was to put the whole mission on hold for two years until a new launch window for Mars opened up as it swung around again into a favorable position for a heliocentric transfer orbit (HTO).
Using this lesser vehicle meant that they could not launch directly into an HTO to Mars, but rather had to enter Earth orbit and use several orbit-boosting maneuvers, taking advantage of Earth’s gravity, to increase their orbital height and energy. The fourth burn fell somewhat short and required two additional burns. By the sixth burn they had achieved an orbit of 192,000km (119,300 miles) and were ready to break orbit and head to Mars.
The practical upshot to all this time in orbit (a total of four weeks) was the opportunity to test all the onboard systems without the added inconvenience of time delays as the ship moved further away. Knowing everything was prepared and functioning provided added assurance that they were ready. One last burn and they were on their way.
From Earth to Mars
Once on the way, there was a new difficulty to overcome. The propellant used is a two-part liquid-fuel system with hydrazine based monomethylhydrazine as the reactant and utilizing dinitrogen tetroxide as the oxidizer; the problem is that it is highly corrosive once mixed, and the piping to deliver fuel to the engine could fail, venting all the fuel to space. The plumbing was never designed to sit idle for ten months with vestiges of fuel in the lines, so the ISRO, very cleverly, added a parallel set of fuel lines. Once MOM was safely on course, pyrotechnic charges disconnected the pipes, and connected the second set, which were left clean and empty of fuel.
Approximately forty hours out from Mars, the IRSO fired the LAM (Liquid Apogee Motor, the ship’s main propulsion system) for less than four seconds, which was sufficient to get telemetry saying everything was functioning nominally.
This engine is capable of generating 440 Newtons (N) of force (about 100 lbs). If the engine had failed, the eight maneuvering engines (22N each/5lbs) would have been used over a much longer timeframe (hence the early test of the main engine), and the orbit could still have been achieved. It seems the Indians had contingencies for the contingencies! Now that’s the way to engineer a system.
The smaller maneuvering engines are operated in what is called a blowdown mode, but can be operated in impulse mode as well. In blowdown mode, the fuel tank is pressurized with a gas (via a bladder) so that fuel can be fed at a steady rate to the reaction chamber to create a continuous thrust as needed. In impulse mode, duration can be as short as 0.8 seconds. These thrusters are capable of continuous operation of 10,000 seconds (166 minutes) before necessitating shutdown, and are rated for a total of 70,000 seconds reliably. In impulse mode they are rated for 300,000 impulses. In other words, these are sturdy reliable engines, and ISRO has used them before for their Lunar orbital mission.
The whole mission was a technology demonstration – so much so that the actual observation of Mars and gathering science data was listed as a Secondary Objective of the mission. The building of the craft, its launch, its three-hundred-day journey, the proper acquisition and entry into orbit, and now preparing to perform the science portion of the mission, made it a phenomenal success.
The PSLV limited the payload to about 14 kilograms (31 lbs), but that includes several instruments that can parallel and compliment the data collected by MAVEN. NASA and ISRO have agreed to share the aggregate data.
Interestingly, MAVEN came up short by not having a Methane Detector; this is an instrument many consider vital to the atmospheric study and determination about the methodology and timeline of the atmospheric loss. Luckily, MOM decided to bring one along.
MOM’s Science Package
- Methane Sensor for Mars – MSM (the equipment missing from NASA’s MAVEN)
- Thermal Infrared Imaging Spectrometer – TIS (for mapping the surface composition of Mars)
- Lyman Alpha Photometer – LAP (measuring atomic hydrogen in the atmosphere)
- Martian Exospheric Neutral Composition Analyzer – MENCA (exospheric neutral density and composition analysis)
- Mars Color Camera – MCC (any time you take a trip, bring your camera for photos!)
The MSM is a highly accurate device capable of scanning for methane across the visible face of the entire planet in a very few minutes (five or ten). It possesses sensitivity in the PPB (Parts Per Billion) range. For those who are technically inclined, it uses multi-beam interferometry in the wavelengths of 1,642 to 1,658 nanometers. It can scan as the weather and seasons change, noting how the methane levels change.
Currently we’re unsure if the methane is generated biologically or areologically (like “geologically” on Earth), or by chemical reactions between iron oxide, carbon dioxide and hydrogen components in the soil. Hotspots have been observed on the surface which have long plumes of methane, and they fade over time. Methane is CH4 and could arise spontaneously in all of these ways.
The TIS is capable of analysing thermal signatures to determine mineralogical composition of the soil. Knowing where useful elements are located will be of aid to future explorers that need to live-off-the-land.
The LAP differentiates between Hydrogen and its heavier cousin deuterium. Atmospheric erosion will leave more of the heavier deuterium behind while stealing the hydrogen. This can generate a timescale to show when the erosion took place and possibly help extrapolate the speed of the depletion.
The MENCA unit is complex, but in its simplest form, it is a mass spectrometer (quadrupole) capable of very fine differentiation in the radial, diurnal, and seasonal variations in the Martian exosphere by neutral-charge atoms with Atomic Mass Units (amu) between 1 (hydrogen) and 300. MAVEN possesses a larger unit but it can only go up to 250amu.
The MMC will dynamically monitor events on Mars such as dust storms, deposition and sublimation of CO2, and any other transient phenomena. It’s a three-color camera, with good resolution of four million pixels (2000 x 2000) across the 400-700 nanometer range. At closest approach it images at 25km x 25km (15.5 x 15.5 miles); at furthest distance in its orbit, the image is 8000 x 8000 km (5000 x 5000 miles).
Thanks, India for your efforts. I hope the monetary markets of the world reward you for your efforts and make India much wealthier overall so that you can increase the standard of living for all of your citizens.
The naysayers that oppose this, and other scientific endeavors, are wrong. The cost of this mission is the equivalent of one bus fare for every Indian citizen. The rewards for the (so far) perfectly executed mission will bring in many, many times the initial investment in foreign capital and new jobs for the people.