Mission Update - July 2004
Over the last month, the science team has conducted a very detailed review of the sequence for taking data from the time of release of the impactor from the flyby until the end of look-back imaging after the impact. This led to several minor changes that should improve the science and better optimize the data that are sent back in near-real time. There are still some uncertainties due to uncertainties in the reflectivity of the nucleus and the brightness of the dust. There are also uncertainties associated with the orientation of the nucleus during the encounter. Other than these two issues, we are confident that we have a robust sequence for taking data.
In parallel over the last month the science team has been studying the data on Tempel 1 that were obtained recently from the Hubble and Spitzer observatories. These will lead to a far better determination of the reflectivity of the nucleus, of its rotational period, and of its axial ratio (degree of elongation, assuming a simple, elliptical, cross section). This analysis should be complete within the next month. Over the longer term, these same data will also provide substantial new constraints on the actual, 3-D shape and on the orientation of the rotational pole, but this requires substantial additional analysis and we do not expect to have this analysis complete until considerably later.
The spacecraft, flyby and impactor joined together and including all the instruments, have just completed the system thermal-vacuum tests with no major problems discovered. These tests were carried out in the largest vacuum chamber available at Ball. The tests involved operations at a very high temperature and then at a very low temperature and then again at a high temperature. A few minor problems are being taken care of but overall there were remarkably few problems discovered and we view the thermal tests as a great success. The combined thermal-vacuum test followed the series of other environmental tests that were described last month by Monte Henderson. The impactor will undergo a separate thermal vacuum test at a later date because its thermal behavior in free flight is expected to be quite different from its behavior when much of it is buried inside the flyby spacecraft.
