Friday, November 14, 2014

Philae vs. MIP (Moon Impact Probe)

Key words: Philae, Rosetta, Moon Impact Probe, Chandrayaan-I

Today (14th Nov., 2014), exactly six years ago "the messenger from India" (as president Kalam called it) Moon Impact Probe had crash landed near Shackleton crater, very close to the south pole of the moon. While 2-days ago we hear about Philae probe of Rosetta space craft of ESA landing on the Comet P67 and hence the title of this post; by no mean there could be any other analogy in these missions. Let me narrate few amazing facts about Philae then will switch over to my own personal experiences as a core-science team member of Moon Impact Probe mission in Chandrayaan-I.


Credit : ESA
The team of Rosetta waited for almost 10-years in chasing the P67 comet before they could send 100-kg Philae to set its foot on the tiny nucleus which was measuring just around 4-km. The mind boggling numbers of 500-million km journey lasting 10-years and sailing along side the elusive comet's nucleus at a distance of few-100s of kms  with a speed of 64,000 km/hr were all truly hair raising statements.

On 12th Novemeber, 2014, the time had just been ripe for the team Rosetta to fire the Philae weighing 100-kgs and would take around 8-hours to be ready to land on the nucleus. As it reaches the nucleus of the Comet, Philae would fire 2-harpoons and would tag itself onto the soft surface. The press reports (from ESA officials) confirm that the Philae has in fact bounced twice and later got settled at location which is not known for sure as of today (14th Nov., 2014); however finds itself in a shadow of a cliff shown below.

Credit: ESA
Though the fully charged battery of Philae would permit its 9-instruments to operate for 56-hours; but the recharging would take much longer than the expected time as the present location would offer only an hour of sunlight for the solar panels to charge the battery; this is certainly not the dead end, as the comet itself would offer its "seasons" where the same location could hope to get much more sun exposure in the future. It is indeed a moment of pride for the entire humanity that the ESA has achieved for the first time on being on a comet. The scientists are upbeat about Philae (though landing on 2-legs, out of three) being very healthy as far as running of their proposed battery of experiments are concerned. Any further manoeuvrability need to be done with extreme care as this may lead to dislodging of the probe from the surface itself. Why... because the the 100-kg Philae would weigh just around 1-gram due to a reduction of gravitational pull of P67 of the order of 100000 less as compared to earth.

Moon Impact Probe (MIP):

Mission: While Phiale's mission is just like a scene picked from a Hollywood movie; Moon Impact Probe was a hard work of a small group of scientists from southern tip of India and their aim was ONLY to drop a 30-kg mass on the southern tip of moon. The mother space craft (red), Chandrayaan-I would re-orient to accommodate MIP separation. During this time the MIP (green) would be detached and in a "pre-programmed" sequence would fire de-orbit motor to reduce the forward velocity component while a set of thrusters fitted on the side would spin-up the probe to attain a stable descent journey. The selected target was close to the Malapert Mountain near the south pole of the moon.

MIP mission; Credit: ISRO
The MIP mission as it was called in the Chandrayaan-I project was the brain child of President Kalam, as per his vision "let there be a messenger reaching moon from the Indian soil". This idea was to be realised at ISRO's Vikram Sarabha Space Center, VSSC. Traditionally at ISRO's VSSC; it has been the hub of developing and realising the rockets, while the idea of MIP which comprises of an autonomous power, communication and instruments can almost be treated as a stand alone space craft. This was a unique experience for the entire group of MIP developers. The objective of MIP was a "Technology Demonstration" which means all other issues (science) would take a back seat; however, the development of a science instrument (CHACE) in this mission with its members having least amount of experience were entertained by the core group of scientists; which allowed us to pull-off one of the most sensitive instrument (CHACE) to study the nearest heavenly body. The plan: the MIP a cuboid of 1/2-meter size weighing around 30-kg would be detached from the mother space craft in the very first opportunity of Chandrayaan-I achieving its 100-km polar orbit.

Moon Impact Probe; Credit : VSSC-ISRO
The MIP would carry 3-experiments during its approximate 22-minutes descend journey. 1. CHACE, (link) the mass spectrometer would sample the nearby ambiance in 1-100 atomic mass range, 2. Color Camera would take pictures and 3. Radar altimeter would measure the distance from the lunar ground. Details of CHACE are narrated here.

It was on 14th November, 2008 around 8.22 pm IST that we were all waiting for the confirmatory signal from MIP which would actually cease to exist (meaning "die down"). It indeed happened and the sacrifice of MIP (that is crash landing) has brought immense wealth of data. The color camera sent stunning pictures as MIP was descending; while CHACE spectrometer measured almost a dozen gaseous species with the peak at 18 representing water standing very very tall indicating the presence of water unambiguously.

MIP landing; Credit : SAC, ISRO
It was no ordinary feat for the MIP team members to design and develop a probe from scratch in a span of just around 4-years and achieve an amazing piece of success in the form of landing the probe within 2-kms of intended location.

Lunar water; Who dunit ??