Thursday, September 24, 2009

Water on the Moon

CHandra’s Altitudinal Composition Explorer, CHACE captures lunar elemental composition

!! A giant step forward for ISRO with a team of 4-5 people who built CHACE from scratch !!

For a quick review on this instrument please visit : CHACE 

Why water is so precious?? Obviousely.. for the human colonisation water plays a crucial role. An estimate from NASA puts a price tag of 50,000 dollars for one liter of water on the moon.

A billion aspirations of Indians reached their pinnacle point when the Moon Impact Probe (MIP) successfully impacted on the Southern pole of Moon on 14th November 2008. It was mooted by none other than the father of Indian Rocketry who sowed the seeds of space research in Inida, the then president Dr. Abdul Kalam. He had told that we should be embracing the moon, instead of merely circling around it. That is how the idea of MIP came into its existence and true to its nature the country today came to the lime light due to its IT prowess has catapulted itself into the elite club of Super Space Nations. Having successfully proved itself as the most reliable rocket (PSLV) in its arms ISRO the premier Indian space agency accepted the challenge of sending a space craft to the moon again relying on its most trusted work horse, PSLV.

The Moon Impact Probe carried 3-payloads, weighing just around 33-kgs, 1. color camera for imaging the moon from the close range as the impactor descends, 2. radar altimeter to measure the altitude to be utilized in the future landing machine and a unique state-of-the-art 3. quadrupole mass spectrometer to sample the lunar ambience in 1-100 amu range. It was a daring effort for the team members at Space Physics Laboratory, Vikram Sarabhai Space Center-ISRO, Trivandrum to develop something which they had done it some 20-years ago during earth's ionospheric studies program.

Within ISRO, the CHACE instrument was something like a crazy idea where just a group of 4-5 people would attempt to build the payload from the scratch. It was huge task to be accomplished in a period of 3-years.

A state-of -the-art quadrupole mass spectrometer (CHACE) was chosen to perform the job of sampling the lunar ambience as the MIP descends. It weighs only 3.3-kg and consumes a meager amount of 20W for having three best possible pressure detectors covering atmospheris pressures(760 torr) to 10(-14) torr. It can measure elements in gaseous phase in 1-100 amu range with an adequate resolution of 1-amu.

Very first challenge was to prepare an instrument which can measure a particle concentration in the range of 10,000/cc. thanks to the prsent day technology the instrument does exist which can do the job. The next task was to check the available sensitivity of the instrument on the ground; this puts a great demand of setting up of a ultra high vacuum laboratory which can create a vacuum in the range of 10(-10) torr.

The second challenge was to make the instrument robust enough to withstand the un-imaginable vibrational forces (~ 25.0g) and to survive the harsh thermal and radiational environment prevailing on the moon. A series of tests were performed to bring a Qualification Model (QM) of the instrument. Though the QM would give 70% satisfaction to the developers the remaining 30% job of preparing a Flight Model (FM) is equally challenging and exciting. Any failure during the short available time of FM development would amount to going back to square one.

The CHACE instrument did throw many many challenges all along the developmental stages; it was only due to the tiredless and focussed effort of 4-5 team members that the realisation of FM was possible.

It was on 15th August 2008 that the Flight Model was handed over to space craft assembly team. The next land mark date was 22nd October when we saw our baby taking plunge towards the most beautiful heavenly body.

Our heart beats were moving faster than any racing car on 14th November when the Moon Impact Probe had its successful journey and eventually crashed near the southern lunar pole. Though we all had lost our baby, but the it has done its job to the perfection. Nobody had ever imagined that a team of 5-people with only one senior colleague having had experience in building space probe could achieve which was comparable rather superior than any other mass spectrometer ever to leave the earth.

Today, 26th September, we are on the seventh cloud as our baby is vindicated by the fact that its sacrifice has not gone waist; as our results will certainly be accepted ONE day. Of course all my team members are cherishing every moment.

-Dr. S.M. Ahmed*, Project manager, CHACE payload

*Presently at University of Hyderabad (

CHACE team:

1. Prof. R.Sridharan, Paylaod scientist

2. Dr. S.M. Ahmed*, Project manager

3. T.P. Das

4. P. Sreelatha

5. P. Pradeep Kumar


  1. Wonderful article, sir........ keep on posting. People would enjoy these sort of articles....write more ....

  2. CHACE (Chandra's Altitudinal Composition Explorer) was a mass spectrometry based payload onboard the Moon Impact Probe (MIP) which sampled the lunar neutral atmosphere in the range of 1 to 100 amu during the descend phase of the same until it impacted at the Lunar South Pole. This was the first in situ measurement of Lunar neutral atmospheric composition in the sunlit side. The CHACE payload detected water vapour in moon's environment by direct in situ measurement. This was an open question till now....... this 'discovery'-class of finding has answered that. The Moon Mineralology Mapper (M3) got the signature of water in ice form, by remote sensing technique. It mapped 97 % of the lunar surface, while CHACE made the observation only along a given meridian. Hence these two complementary measurements confirmed the presence of water on Moon.