India PSLV successfully launches MOM en route to Mars

by William Graham

India launched its first interplanetary spacecraft Tuesday, with a Polar Satellite Launch Vehicle sending the Mars Orbiter Mission on its journey to the red planet. Liftoff of the mission, which also marked India’s fortieth orbital launch and the twenty-fifth flight of the PSLV, was on schedule at 09:08 UTC (14:38 local).

India’s Mars Shot:

The Mars Orbiter Mission, or MOM, is the first Indian mission beyond Earth orbit and comes a little over five years after the Chandrayaan 1 spacecraft was launched to the Moon. The Mars mission, which has been nicknamed Mangalyaan by some outside ISRO, is expected to arrive in areocentric orbit on 24 September next year.

MOM is based on a derivative of ISRO’s I-1K satellite bus, a platform first used for the METSAT-1 weather satellite launched in September 2002.

Z4In February 2003, four days after her death aboard the Space Shuttle Columbia, the satellite was renamed Kalpana 1 after astronaut Kalpana Chawla.

Designed to operate for seven years, Kalpana 1 is still in service at 74 degrees east. The I-1K bus was also used for the GSAT-12 communications satellite launched in 2011 and for India’s IRNSS-1 navigation satellites, the first of which was launched in July this year.

MOM also draws upon hardware developed for INSAT and Indian Remote Sensing satellites and the Chandrayaan 1 mission.

The spacecraft carries a bipropellant engine to achieve insertion into orbit around Mars. It is fuelled by monomethylhydrazine, and oxidised by dinitrogen tetroxide.

Z3The propulsion system is derived from that used for several previous geostationary satellites as well as the Chandrayaan 1 mission; however it has been modified to improve its reliability and ensure that it can still be operated after the ten month coast to Mars.

The main engine delivers 440 newtons (45 kgf or 99 lbf) of thrust and will be fired to propel the spacecraft out of Earth orbit and again for orbital insertion once the probe reaches Mars. Eight smaller thrusters, delivering 22 newtons (2.2 kgf, 4.9 lbf) each, will be used for attitude control.

MOM has a dry mass of 488 kilograms (1,080 lb). It carries 852 kilograms (1,880 lb) of propellant, giving it a mass at launch of 1340 kg (2950 lb). One solar array, consisting of three panels, will be used to generate electrical power for the spacecraft; it is expected to produce around 840 watts. The solar array will charge a lithium ion battery, with a capacity of 36 amp-hours.

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Communications to and from Earth will be made in the S-band, with low, medium and high-gain antennae mounted on the spacecraft to ensure that it can transmit and receive signals. These will provide transfer rates of up to 40 kilobits per second.

Data will be downlinked via the Indian Deep Space Network’s 18 and 32 metre (59 and 105 feet) antennae at Bangalore, and through NASA’s Deep Space Network. Additionally, during the early stages of flight the ISRO Telemetry, Tracking and Command Network will be used to relay data between the spacecraft and Earth, while two tracking ships have been stationed in the Pacific Ocean to track the launch up to spacecraft separation.

Z6The Mars Orbiter Mission spacecraft carries five scientific instruments: the Mars Color Camera; Thermal Infrared Imaging Spectrometer; Lyman Alpha Photometer; Methane Sensor for Mars and Mars Exospheric Neutral Composition Analyser.

The main imaging payload aboard MOM is the Mars Color Camera (MCC), a three-colour imager which will be used to study the surfaces of Mars and its two moons, as well as providing visual images to compare with data returned by other payloads. The Thermal and Infrared Imaging Spectrometer (TIS) will study the infrared spectra of areas of the Martian surface, determining its composition and allowing maps to be produced showing the presence of minerals in the surface.

The Lyman Alpha Photometer (LAP) and Methane Sensor for Mars (MSM) comprise the spacecraft’s atmospheric payload. LAP is designed to measure the amount of hydrogen-2 (deuterium) in Mars’ atmosphere, relative to the abundance of hydrogen-1.

Z8This will be achieved by studying the ultraviolet spectra of emissions from the Mars’ upper atmosphere, and looking for a small shift in the Lyman-alpha line; a spectral line resulting from energy emitted when an electron goes from the first excited state to its ground state.

Data on the proportions of hydrogen-1 and deuterium will help scientists to understand how the water once present on Mars has escaped from the planet’s atmosphere. The Methane Sensor for Mars studies reflected sunlight to deduce the presence, location and abundance of methane in the atmosphere.

The fifth instrument, the Mars Exospheric Neutral Composition Analyser (MENCA), consists of four mass spectrometers which will be used to produce in-situ data on the uppermost region of Mars’ atmosphere: its exosphere. The instrument, which is derived from the CHACE experiment on the Moon Impact Probe – a small impactor released by Chandrayaan-1 – will study the composition by mass of the Martian exosphere.

Z9The Mars Orbiter Mission will, if it reaches Mars successfully, make India the first Asian country to have a spacecraft orbiting the red planet. Japan and China have both attempted missions to Mars; Japan with Nozomi in 2003, and China with Yinghuo-1 in 2011; however both missions failed.

Nozomi failed to reach Mars after a series of propulsion and electrical failures, while Yinghuo-1, which was launched attached to Russia’s Fobos-Grunt probe, was lost after its mothership failed to depart low Earth orbit.

Three orbiters are currently in operation around Mars; NASA’s Mars Odyssey and Mars Reconnaissance Orbiter, and ESA’s Mars Express. A further two spacecraft are operational on the surface: the Opportunity rover is in Endeavour crater and Curiosity is exploring Gale crater.

In addition to the Mars Orbiter Mission, these spacecraft will also be joined next year by NASA’s MAVEN orbiter, which is scheduled for launch atop an Atlas V rocket later this month.

PSLVThe Mars Orbiter Mission began with a launch aboard India’s Polar Satellite Launch Vehicle, flight number C25, from the First Launch Pad at the Satish Dhawan Space Centre. The mission, which marked the twenty fifth launch of a PSLV and the fifth flight in the PSLV-XL configuration, was India’s fortieth orbital launch.

India had originally been expected to reach this milestone in August with the launch of GSAT-14 atop a Geosynchronous Satellite Launch Vehicle, however that flight was delayed to December after a fuel leak was detected shortly before liftoff.

The Polar Satellite Launch Vehicle was primarily developed to deploy satellites into polar and sun-synchronous low Earth orbits. Replacing the Augmented Satellite Launch Vehicle (ASLV), the PSLV made its first flight in September 1993, however it failed to achieve orbit, with the rocket going off course and being destroyed by range safety.

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The first successful launch came in October 1994, with the IRS-P2 satellite. Since then only one other launch has failed; the first operational flight in September 1997 left IRS-1D in a lower-than-planned orbit.

Z10The PSLV is a four-stage rocket, with the first stage augmented by six solid rocket motors. Three configurations have been flown, which differ in terms of the boosters used on the first stage: the standard PSLV uses PS0M boosters with S-9 motors, the PSLV-XL uses PS0M-XL rockets with more powerful S-12 motors, and the PSLV-CA configuration omits the boosters altogether for missions which do not require as much performance.

The PS0M-XLs used during Tuesday’s mission contained 12.2 tonnes (12 imperial tons, 13 US tons) of propellant, generating 719 kilonewtons (73,300 kgf, 162,000 lbf) of thrust and burned for fifty seconds.

The first stage of the PSLV, the PS1, is powered by an S-138 solid rocket motor. This stage was introduced on the fourth PSLV launch; the first three flights used a less capable S-125. The numbers in the solid rocket motor designations denote the mass of propellant they contain; in the case of the S-138 that indicates 138 tonnes (136 imperial tons, 152 US tons). It generates 4,800 kilonewtons (0.49 million kilograms-force or 1.1 million pounds-force) of thrust.

Three seconds before the scheduled launch, the first stage reaction control system engines ignited, with first stage ignition coming when the countdown reached zero. The four ground-lit solid rocket motors ignited in pairs two tenths of a second apart, at 0.46 and 0.66 seconds into the mission.

The PSLV will launched and begin its ascent towards orbit, rolling to a heading of 104 degrees. At 25.04 seconds after liftoff, the two remaining solids lit.

The ground-lit solid rocket motors burnt out around 50 seconds after liftoff; separating in the same pairs 69.28 seconds after they ignited. The air-lit motors burnt out at around the 75-second mark, with separation 92.04 seconds into the flight.

Z22The first stage continued to burn for 103 seconds, with its extinction followed by a short coast phase to allow any transient thrust to subside. 112.75 seconds after liftoff, the spent stage separated, with the second stage igniting two tenths of a second later. Five seconds after stage two ignition the rocket initiated closed-loop guidance.

The second stage of the PSLV, the PS2 or L-40, is liquid-fuelled burning UH25 – a mixture of unsymmetrical dimethylhydrazine (UDMH) and hydrazine hydrate – and dinitrogen tetroxide. It uses a Vikas engine, derived from France’s Viking engine which was used on early Ariane rockets, up to the Ariane 4. The stage carries 42 tonnes (41 imperial tons, 46 US tons) of propellant, generates 799 kilonewtons (4,280 kgf, 9,440 lbf) of thrust and burned for 148 seconds.

The payload is enclosed within a 3.2-metre (10-foot) payload fairing, which separated from the vehicle around 88.80 seconds into the second stage burn. A minute and three seconds later the second stage separated, having shut down its engine approximately three seconds beforehand.

Third stage ignition, which was timetabled for 1.2 seconds after staging, began a 112-second burn for the vehicle’s solid-fuelled HPS3 third stage. A lengthy coast phase followed the end of the third stage burn.

Nine minutes and 43.6 seconds after liftoff – a little over 200 seconds after third stage burnout – the third and fourth stages separated. Fourth stage ignition did not occur until 35 minutes after launch, with the burn scheduled to last eight minutes and thirty nine seconds. However, due to some over-performance – resulting in lofting – the burn was slightly less than planned.

The fourth stage, the PS4 or L-2.5, was another liquid-fuelled stage burning monomethylhydrazine and mixed nitrogen oxides. It carried 2,500 kilograms (5,500 lb) of propellant and was powered by two engines each generating 7.3 kilonewtons (740 kgf, 1,600 lbf) of thrust.

With the completion of the fourth stage burn, the PSLV’s role in the mission was complete, and all that remained was for it to deploy the Mars Orbiter Mission spacecraft to begin its mission.

Spacecraft separation took place over the Pacific Ocean, 44 minutes and 17 seconds after liftoff or 37 seconds after fourth stage burnout.

Z5The target trajectory for spacecraft separation was an elliptical medium Earth orbit, with a perigee of 250 kilometres, an apogee of 23,500 kilometres (155 by 14,600 miles, 135 by 12,700 nmi). The orbit is inclined at 19.2 degrees to the equator, with an argument of perigee of 282.55 degrees.

From its parking orbit, MOM will perform a series of six manoeuvres using its main engine to raise itself into higher transfer orbits. On 30 November it is expected to achieve escape velocity, entering heliocentric orbit. Following a ten-month coast arrival into orbit around Mars is targeted for 24 September 2014.

The planned areocentric orbit has a periareon of 365 kilometres, an apoareon of 80,000 km, (227 by 50,000 miles, 197 by 43,000 nmi) an inclination of 150 degrees and a period of 76.7 hours.

The launch of PSLV C25 with MOM marked the third orbital launch for India in 2013, following the February launch of SARAL and the July launch of IRNSS-1A, both of which used PSLV rockets. Tuesday’s launch is the last PSLV launch of the year, and the penultimate orbital launch of the year for India.

The next Indian launch is currently scheduled for 15 December, with the Geosynchronous Satellite Launch Vehicle returning to flight with the much-delayed deployment of GSAT-14.

(Images via ISRO and Various Indian News Feeds).

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