The flyby distance will not be decided until this autumn, and is likely to be adjusted until the very end as Earth astronomers try to measure the size and density of the dust cloud around the comet during its next perihelion passage.

The flyby distance will certainly be at least several hundred kilometers, and is likely to be as much as one or two thousand km - which would still allow very good nucleus photos.

Second, there is -- once again -- the problem of accurately pointing the craft's cameras at its target. Ground controllers think they now thoroughly understand AutoNav's problems during its Braille flyby, and that they could have accurately steered DS1 to a flyby within 10 km of Wilson-Harrington and pointed it accurately during that flyby.

But DS1's cameras will see Borrelly's nucleus against the glowing backdrop of the comet's coma -- and since comet nuclei are quite dark in color, scientists are not certain whether to program AutoNav to look for a bright object against a dark sky, or a dark object against a brighter sky (as turned out to be the case with Halley).

This will be debated for some time. The current favored solution is to wait until DS1 is close to the nucleus before turning on AutoNav's target-tracking capabilities. Alternatively, AutoNav the targeting system may not be used at all.

Instead, DS1 may simply rock its viewfield slightly back and forth during the flyby to build up a mosaic, some of whose frames will be certain to contain the nucleus -- a technique that was used with complete success by the Galileo and NEAR spacecraft to photograph the asteroids which they flew past.

Finally, there are the problems with the spacecraft's science instruments. DS1's second instrument -- PEPE -- is another "new technology" device. A miniaturized 6-kg package PEPE combines plasma analyzers, to measure the energy and flow direction of ions and electrons, with an ion mass spectrometer, that can analyze the chemical composition of ionized molecules up to 500 AMU.

It worked perfectly during the first part of the mission -- analyzing the exhaust of the craft's ion drive and sniffing for any gases given off by Braille during the closest part of its flyby. It found none, but that was expected.

But in November, shortly before the star tracker failure, PEPE suffered an apparent short circuit of its own which is hindering the ability of its mass spectrometer to analyze heavy molecules -- including the complex and scientifically important organic compounds thought likely to exist in the gases of Borrelly's coma.

Combined with the failure of the ultraviolet spectrometer, this will seriously hinder the ability of DS1 to analyze Borrelly's chemical composition -- one of the flyby's most important goals.

Still, the flyby is very much worth doing. DS1's cameras, including the Active Pixel camera, whose limitations can be compensated for and which can send back pictures at a higher rate than the CCD camera will send back pictures of the comet's nucleus and the violent jets of material spurting out of it with a resolution of only a few dozen meters per pixel, far better than Giotto's photos although DS1's pictures will all be in black-and-white.

Observations of Borrelly's nucleus by the Hubble Space Telescope indicate that it is an elongated object like Braille -- over twice as long as it is wide -- but a good deal bigger: about 4 by 9 kilometers. It is thus likely to look very different from Halley's nucleus.

Moreover, even at a distance of 1000 km, it would completely fill the viewfield of the Active Pixel camera.

Also, DS1's near-infrared spectrometer, which is still working perfectly, should be able to provide important data both on the mineral makeup of the nucleus and on the composition of many of the gases in Borrelly's coma.

Meanwhile PEPE, despite its limitations, should be able to provide excellent data on the way in which Borrelly's gaseous emissions interact with the solar wind flowing past the comet, as well as a good deal of chemical composition data.

So -- like the Galileo spacecraft orbiting Jupiter -- Deep Space 1 preserves on with its mission. Despite severe communication problems, Galileo has provided a huge amount of invaluable scientific data about Jupiter and its moons, simply because its controllers were unwilling to give up on it.

DS1 has already achieved its primary goal of testing revolutionary new space exploration technology using a "better-faster-cheaper" mission, and most of that new hardware worked very well.

Even the MICAS problems are well enough understood now that the device is a major candidate to become the main scientific instrument on the 2004 Pluto flyby probe.

With a dash of luck and plenty of skilled navigation, Deep Space 1 will survive another two years and emulate Galileo by providing important new scientific data about the Solar System.

Deep Space 1: Rocketing to the Future

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Satellite Launch To Boost DTH In India
Calcutta, India (SPX) Dec 28, 2005
The successful launch Thursday of India's heaviest satellite from spaceport of Kourou in French Guyana may have boosted the country's space research efforts to yet another level, but it has also lifted the spirits of at least three Direct-To-Home televisions broadcasters, one of which has been waiting for years to launch its services in India.