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.

Philae:

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.


Friday, August 22, 2014

Comet Siding Spring visit of Mars

The space enthusiasts around the globe were preparing for an exciting moment: on how the two visitors from earth would be able to make it to planet Mars in the 3rd week of September. The team at NASA was quite confident on their 485 million dollars worth baby, MAVEN; while the Indian-MOM ($ 75-millions) was carrying ONE billion hopes to be able become the FIRST country to make it on their first attempt to planet Mars. Suddenly the focus has shifted to an event which would occur a month later, truely a Cosmic Spectacle which is going to take place if you were to be on Mars on Oct.19th. The comet Siding Spring will be zipping past almost at a distance of 1/3rd of that of earth-moon.
Comet on MARS (artist's view)
Credit : Viral Global news 
When the Indian Mars Orbiter Mission, MOM was getting ready; there were few whispers around on the suspected visit of an intruder on Mars (indicating whether the mission should go ahead ???) ; credit to the think tank of ISRO that they went on record to announce that the mission is ON. In one of my earlier posts (link), on my personal behalf I had predicted that even if the comet were to make it; this would offer a life time opportunity to study this event. This is precisely what has been the mood all around the globe today.

What is the fuss all about this event:
Orbiters, Rovers of NASA on MARS
Credit : NASA
It is a rare among rare opportunity that the space scientists would be getting to study a comet at such a close range. Siding Spring, a long period comet making its visit for the first time to the solar system has stirred huge interest among scientists and a common man. The good news: as per recently carried out modelling study (JPL and few other university teams) on comet's path around the solar system, the comet's nucleus with a size of around 2-kms will be moving within a distance of 132,000 kms from the planet; even then it is 17-times closer than the nearest recorded comet (L1 Lexell, 1780) in history. At this distance both the ion-tail and the dust tail is going to miss the Mars. The bad news: is all due to a trail of dust particles which would be moving at a very high relative speed of around 57-kms per second during the closest visit of this comet; this would start 90-minutes before and would be lasting for another 20-minutes of actual passing time. As per the estimate of scientists, at these speeds even a tiny dust particle of half millimeter size could cause appreciable damage; "essentially they pierce the skin of any satellite; they would be like bullets, out there" quoted by Rich Zurek of JPL. Presently there are two orbiters: Mars Odyssey, Mars Reconnaissance Orbiter and two rovers: Opportunity, Curiosity of NASA while one orbiter from ESA: Mars Express. The fuss is all due to the devastating effects this unexpected visitor to Mars would be causing; but... hey.. hang on.. this has now become a talking point on every possible popular scientific forum... because the fear of damage to the probes is turning into excitement of observing this unique phenomenon.

Ducking behind Mars:
Credit: NASA
The scientists at NASA have already come up with a plan of taking their orbiters behind the Mars planet during the passing-by phase of the trail of cometry particles. Both the orbiters of NASA have gone through the first level of orbit correction; they have also indicated that the newly arriving MAVEN would also be placed in an appropriate orbit to be placed itself behind the planet during the comet's transit. While the Indian team at ISRO is yet to make an official announcement to this effect.  However, the scientists at NASA believe that the rovers on the ground will be under least amount of facing any kind of hazard and hence have not opted any protective measures.

Observations for the spectacle:
Comet tails: explained
Credit : NASA
Though this may lead to a technical discussion (and hence elaborations are avoided); the indications leading us to believe that the NASA team has made elaborate arrangements in terms of preparing the suitable instruments on their orbiters and rovers to be ready for the cosmic spectacle to study the : comet/coma as such, coma-mars atmosphere interaction and also formation of Martian Aurora which may occur due to the interaction of coma and higher part of Martian atmosphere, as pointed out by David Brian, LASP, Univ of Colorado. Last but not the least, we, here in India will also be cheering for the MOM to catch up with the huge amount of opportunities which are thrown open during the nature's display of fire show.

Curious observation (Author's take) :
DEIMOS: images taken by MRO
Credit : NASA
The object which is furthermost away to planet Mars and still part of it is Deimos, the second moon, is going to take a heavy beating on October the 19th. Poor Deimos with a diameter of around 13-km which has been spending very quite time all around, but situated around 23,000 km from Mars would be awake to a violent shower of particles (bullets) both neutral and ions. It will be interesting to note the fate of this object which is having a porous regolith (1.47 gm/cm3) .

Schiaparelli