Tuesday, November 4, 2008

Chandrayaan-1 update 3: Transfer orbit; trajectory questions clarified; camera testing; mapping radioactivity, magnetic anomalies, & water ice; ...

Related: More recent Chandrayaan updates are available.

Sections of this somewhat longish post are ordered from the perspective of science fiction fans; if you are not one, interesting stuff may be down below rather than early in the post.

Mapping magnetic anomalies.

The Martian Chronicles on a Swedish instrument called SARA on board the ship: "SARA will also be able to study magnetic anomalies, presumably because the magnetic fields will change how the solar wind interacts with the surface."

"Magnetic anomaly" caught my attention because this is what begins the fuss in Arthur Clarke's famous novel "2001 A Space Odyssey". TMA it was called in the story - Tycho Magnetic Anomaly, because it was found in the Tycho region.

What's the use of "Radioactive mapping"?

Radioactive mapping is one of the things the mission will do. But what is it? And why do it?

The Martian Chronicles clarifies the purpose of the on board Bulgarian instrument that will do this job: "The whole goal is for this thing to get bombarded with radiation and see how much there is, what range of energies the particles have, and figure out how that dose might change for different locations on the moon. The Apollo astronauts were only out of Earth’s protective magnetic field for a few days, but for colonists spending months or years out there, it’s important to know how much radiation shielding they will need, and what type of radiation is the most dangerous."

Detecting water ice.

The Martian Chronicles on an on board Indian instrument called HEX: "a thick ice deposit would absorb x-rays that normally would be emitted to space, so by measuring changes in x-ray emission, HEX might be able to detect water ice."

Chandrayaan-1 Project Director answers some questions on ship's trajectory.

Technical details of trajectory to moon of Chandrayaan-1 spaceship

Via R Prasad's article titled "How Chandrayaan-1 is raised to higher orbits" in The Hindu newspaper of Madras. Article is based on correspondent's interaction with "M. Annadurai, Project Director of Chandrayaan-1". Click image above for full size original.
[Thanks for link, Dennis]

Why this multistage trajectory? Answer is, primarily, caution: "We could have done it [in] one shot, but there is a possibility of missing the moon. So we have adopted an incremental increase in the orbits’ perigee." I suppose "apogee" is meant, & "perigee" is a misquote.

Also, "There will be a need to correct the orbit once in two weeks to maintain a 100 km circular orbit" on moon. I guess at the end of its useful life - meaning propellant & fuel exhausted - it will simply fall somewhere on moon?
Related: Arthur Clarke's novel "Islands in the Sky" lightly touches upon the subject of human littering in space. A habit now when it doesn't cause much damage but a costly danger when space travel becomes common (because habits die hard). Not that ISRO is alone - everyone traveling to space seems to be doing it today.

Mr Annadurai answers several other questions too, including why fire at perigee & how moon capture will happen.

A related point: Reducing the speed - needed for capture by moon & lowering of orbit there - requires that "the orientation of the spacecraft is reversed — turned 180 degrees". This implies the craft is fitted with special orientation rockets that can fire simultaneously in more than one directions. I'd not thought of it; I guess it's needed by all craft that orbit earth too.

Chandrayaan-1 is now on "Lunar Transfer Trajectory".

Illustration accompanying the ISRO announcement that Chandrayaan spacecraft is now in Lunar Transfer Orbit after the fifth orbit raising

ISRO announcement dated 4 November 2008: "The fifth and final orbit raising manoeuvre of Chandrayaan-1 spacecraft was successfully carried out today (November 4, 2008) morning at 04:56 am IST... With this, Chandrayaan-1 entered the Lunar Transfer Trajectory". Current orbital parameters: apogee = 380,000 km. Perigee not specified in the announcement. Click image for original size picture.

"Chandrayaan-1 will approach the Moon on November 8, 2008". That's when next manoeuvre is due - to transfer it from earth orbit to moon orbit.

Camera testing: Some pictures of earth.

From ISRO announcement dated 31 October 2008: "The Terrain Mapping camera (TMC) ... was successfully operated on October 29, 2008".
Note: IST is India time. 5:30 hrs ahead of GMT, no day light saving adjustments.

Announcement provides 2 black & white pictures of earth (click pictures for original sized images):
  1. "taken at 8:00 am IST from a height of 9,000 km shows the Northern coast of Australia".

    Picture of Northern coast of Australia, taken by Chandrayaan-1 spaceship on 31 October 2008 at 0800 am IST from a height of 9000 km

  2. "taken at 12:30 pm from a height of 70,000 km shows Australia’s Southern Coast".

    Picture of south coast of Australia, taken by Chandrayaan-1 spaceship on 31 October 2008 at 1230 pm IST from a height of 70000 km

I'm puzzled why they published pictures of Australia rather than India. I assume it was engineering considerations, rather than oversight.

"The camera can take black and white pictures of an object" & "has a resolution of about 5 metres." I suppose they meant 5m from a distance of 100 km, the target lunar orbit, & that earth pictures being distributed were at far lower resolution?

Chandrayaan-2 work sharing with Russia clarified.

ISRO Chairman G Madhavan Nair: "The lander will be from Russia... The rover will be a joint development between Russia and India."

Spacecraft, of course, is Indian.

Mapping "the whole moon"!!

In the last update, I'd quoted Narendra Bhandari, a member of the Science Advisory Board for Chandrayaan-1 as saying that one of the mission objectives was "topographic mapping. That will be done for the whole moon at 5m resolution".

I assume he meant it for part of the moon visible from Chandrayaan-1 orbit around it. I mean - it cannot see "the whole moon" from a single orbit. Or do they intend to change orbits during its 2 year duty?

Gossip: Chandrayaan-3 (manned landing in 2015).

I seem to have misplaced a juicy quote from some babu or neta in Delhi that gave me a smile. It appeared in a local newspaper a few days back - I think Indian Express, but I'm not sure.

I interpreted the long winded quote as saying that: Delhi was upset that Chandrayaan-3 was announced publicly by ISRO bosses, & didn't let the neta concerned get publicity! He clarified that the project is not likely to be killed for lack of budget.

Related older report: G Madhavan Nair, Chairman of ISRO: "We are planning to carry two human beings into the space in our first manned space mission... The project outlay is Rs 120 billion".

What next?

  1. All Chandrayaan posts.
  2. All moon posts, including fiction set on moon. A-rated stories probably won't disappoint. For free fiction, search for "full text" (without quotes). Or browse through all free fiction posts, including stories unrelated to moon.
  3. Subscribe to Variety SF master feed, Chandrayaan feed, or moon posts feed.


Ryan said...

"I assume he meant it for part of the moon visible from Chandrayaan-1 orbit around it. I mean - it cannot see "the whole moon" from a single orbit. Or do they intend to change orbits during its 2 year duty?"

I think he meant the whole moon, but not all at once. Chandrayaan will probably be put into a polar orbit, which is what is usually used for global mapping. You just let the planet rotate while the spacecraft's orbit remains "fixed" in space, so each orbit you pass over new ground.

Tinkoo said...

Thanks Ryan. That's a cool technique. I'd not thought of that.