Stardust Mission Status 6 September 2000

NASA’s Stardust spacecraft, launched in February 1999 on a mission to
collect a sample from Comet Wild-2, remains in good health as it travels the
solar system. Engineers and scientists have just completed a series of tests
to see if mild heating will remove some contamination on the spacecraft’s
navigation camera optics, which scatters light and blurs the images. The
navigation camera’s principal function is to help guide the spacecraft on
its final approach to the comet, and the obscuration on the camera is not
expected to seriously impair the main mission of collecting and returning
samples from Comet Wild- 2’s dust tail. However, close navigation to the
comet may change somewhat depending on the results of further testing.

On Monday, Sept. 4, the final images were received from an onboard
test to determine if mild heating alone might clear the camera’s view. A few
months ago, engineers detected that a small amount of an unknown substance
had settled on one or more optical components of the camera. Engineers were
trying to clear the debris by turning on a small heater on a window that
protects the detector. Images showing the contamination confirm that the
camera is “fogged.”

The week-long heater test increased the temperature around the window
from -35C (-31F) to about 8C (47F). Then the camera took pictures of a small
calibration lamp immediately in front of the camera lens, inside the
spacecraft. The blurring shown in the recent images changed from image to
image as the heating progressed.

Engineers hope to better characterize the nature of the blurring by
analyzing navigation camera images of several starfields. Since small points
of light, the stars, will provide a more specific target than the general
illumination from a light source, the starfield pictures should show how the
sharpness of the images has changed after the heating test. Engineers will
analyze the images when the camera data are received from the spacecraft in
late September. The navigation team may perform additional heating and
imaging tests if this seems useful and/or necessary. It is also possible
that there may be contamination on the periscope and/or the scan mirror,
which are external to the lens.

Project engineers say that since the camera was the coldest part of
the spacecraft shortly after launch, it would tend to act almost like
flypaper in picking up any volatile materials coming from the spacecraft
immediately after launch. Investigations into the origin of the coating are
inconclusive.

The camera’s main duty is to guide the spacecraft to the exact point
of closest approach to the comet, and it is also scheduled to take pictures
of the comet. The blurring is not expected to seriously impair the main
science mission of collecting and returning samples from Comet Wild-2’s dust
tail. However, close navigation to the comet may change somewhat depending
on the results of further testing.

Stardust is a Discovery mission, managed by JPL for NASA’s Office of
Space Science, Washington, D.C. JPL is a division of the California
Institute of Technology in Pasadena, California. Visit the Stardust home
page at: http://stardust.jpl.nasa.gov