In This Part Of The Series On The Lunar Mission, TOI Takes A Closer Look At The Spacecraft & Its Path
Srinivas Laxman | TNN
Mumbai: As the moon mission began progressing from the realms of imagination to reality, scientists put their heads together to design the perfect spacecraft to carry India’s soaring aspirations. After slogging it out for months, straddling numerous calculations and combinations, what emerged from the drawing boards was a cuboid spacecraft. It had a single solar array to generate power.
As the spacecraft took shape, the scientists continously monitored its progress on computers. The equipment was housed in a closely-guarded room at the Isro satellite centre in Bangalore. During launch, the spacecraft will weigh 1,304 kg. Once it reaches the lunar orbit covering a distance of nearly 3,86,000 km from the Earth, its weight will go down to 590 kg as most of its
propellants will be depleted during the five-and-a-half-day journey.
Of its total weight, the 11 scientific payloads it’ll carry will weigh 80 kg. Initially, when the design of the spacecraft was conceived, the weight of the payloads was kept at 35 kg. One of the reasons why it shot up was the inclusion of the 29-kg Moon Impact Probe, an Indian payload which was initiated at the instance of former President A P J Abdul Kalam. The probe will crashland on the lunar surface to identify future landing sites and explore the moon from a close range.
After freezing the design, scientists got down to preparing it and, by September, it was in flight mode. But takeoff was still a far cry as the spacecraft had to undergo several crucial tests to assess if it could weather the hostile space environment while encircling the moon for two years. Chandrayaan-I would take 117 minutes for every revolution at an altitude of 100 km above the lunar surface.
In the thermovac test, the spacecraft was lowered into a chamber with temperature extremes. “This test imulates the actual difficult space environment,” said an Isro official.
Next came the vibration test in which the spacecraft was placed on a table and vibrated just like an actual launch. Third in line was the acoustic test where the roar of four jet planes was simulated simultaneously to check if the spacecraft could survive the literal blast of the launch. Isro officials recalled a case a few years ago when a few cows, which had accidentally strayed into the launch zone, had gone deaf because of the sound and fury of the takeoff.
The lunar vehicle scored full marks in all these tests and is now ready for launch in the early hours of October 22. After takeoff, once it detaches from the rocket and enters the geo-stationary transfer orbit at an altitude of about 30,000 km, the spacecraft will operate on its own for a few days.
The spacecraft will generate power through what is known as a canted single-sided solar array. Which means Chandrayaan’s energy will be gathered from the sun. The solar array with lightsensitive cells will generate 700 watts during peak period. During eclipse, it will be powered by lithium batteries.
Chandrayaan is also equipped with various other things like thrusters, which will execute fuel burns to alter the trajectory whenever needed. It has an inertial measurement unit consisting of accelometers and gyroscopes to measure the attitude or direction. Besides, there is a thermal management system to protect it from excessive heat. The design of the spacecraft is so advanced that flight controllers on earth can instruct it to bring a back-up on line if there is a technical hitch. It has three solid state recorders (SSRs) on board to record data from various payloads. While SSR-I will store science payload data, SSR-II will carry spacecraft altitude information, satellite housekeeping and other auxilliary data besides science payload data. The
Moon Mineralogy
Mapper payload has an independent SSR.
As the spacecraft took shape, the scientists continously monitored its progress on computers. The equipment was housed in a closely-guarded room at the Isro satellite centre in Bangalore. During launch, the spacecraft will weigh 1,304 kg. Once it reaches the lunar orbit covering a distance of nearly 3,86,000 km from the Earth, its weight will go down to 590 kg as most of its
propellants will be depleted during the five-and-a-half-day journey.
Of its total weight, the 11 scientific payloads it’ll carry will weigh 80 kg. Initially, when the design of the spacecraft was conceived, the weight of the payloads was kept at 35 kg. One of the reasons why it shot up was the inclusion of the 29-kg Moon Impact Probe, an Indian payload which was initiated at the instance of former President A P J Abdul Kalam. The probe will crashland on the lunar surface to identify future landing sites and explore the moon from a close range.
After freezing the design, scientists got down to preparing it and, by September, it was in flight mode. But takeoff was still a far cry as the spacecraft had to undergo several crucial tests to assess if it could weather the hostile space environment while encircling the moon for two years. Chandrayaan-I would take 117 minutes for every revolution at an altitude of 100 km above the lunar surface.
In the thermovac test, the spacecraft was lowered into a chamber with temperature extremes. “This test imulates the actual difficult space environment,” said an Isro official.
Next came the vibration test in which the spacecraft was placed on a table and vibrated just like an actual launch. Third in line was the acoustic test where the roar of four jet planes was simulated simultaneously to check if the spacecraft could survive the literal blast of the launch. Isro officials recalled a case a few years ago when a few cows, which had accidentally strayed into the launch zone, had gone deaf because of the sound and fury of the takeoff.
The lunar vehicle scored full marks in all these tests and is now ready for launch in the early hours of October 22. After takeoff, once it detaches from the rocket and enters the geo-stationary transfer orbit at an altitude of about 30,000 km, the spacecraft will operate on its own for a few days.
The spacecraft will generate power through what is known as a canted single-sided solar array. Which means Chandrayaan’s energy will be gathered from the sun. The solar array with lightsensitive cells will generate 700 watts during peak period. During eclipse, it will be powered by lithium batteries.
Chandrayaan is also equipped with various other things like thrusters, which will execute fuel burns to alter the trajectory whenever needed. It has an inertial measurement unit consisting of accelometers and gyroscopes to measure the attitude or direction. Besides, there is a thermal management system to protect it from excessive heat. The design of the spacecraft is so advanced that flight controllers on earth can instruct it to bring a back-up on line if there is a technical hitch. It has three solid state recorders (SSRs) on board to record data from various payloads. While SSR-I will store science payload data, SSR-II will carry spacecraft altitude information, satellite housekeeping and other auxilliary data besides science payload data. The
Moon Mineralogy
Mapper payload has an independent SSR.
Pre-launch tests
Thermovac test to assess the spacecraft’s strength against temperature extremes
Vibration test placing the spacecraft on a table and simulating the environment of an actual launch.
Acoustic test simulating the roar of four jet planes simultaneously to see if the instruments survive the blast of the launch.
MOON IMPACT PROBE
A 29-kg Indian payload included at the instance of former President A P J Abdul Kalam. It’s three major components are:
Radar Altimeter to measure the altitude of the MIP above the lunar surface and help in developing technology for future landing missions
Video Imaging System to acquire images of moon’s surface from the descending probe
Mass Spectrometer for measuring the constituents of the lunar atmosphere during descent.
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