\header ENTRY_TIME = 2003 JAN 11 00:01:36 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2002 SEP 03 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text As STARDUST once more approached the Sun and Earth sufficiently to begin some imaging, a first test was made of the new windowing and pattern matching software. Coincident with this, a series of geometric calibration tests was planned, since those of June 2001 were not totally successful. In addition, a calibration lamp image and four full frame fields were acquired at zero and thirty degrees, one of the latter compressed. These were intended as a modestly comprehensive check for contamination, for scattered light, and of compression, a systems check. It was found that there had been a small amount of recontamination in the 10 months since the previous image. This was most obvious in the cal lamp image. Star images remained sharp but with a very shallow skirt of scattered light. The pattern matching and windowing failed at 14 of the 19 angles. At the larger mirror angles there was a problem with increasing scattered light. The windows used were only 21x21 pixels, and it became clear that somewhat larger windows were necessary and that there were still geometric calibration problems. The contamination on the periscope was found to be significantly reduced compared to its state two years earlier. A heating cycle is planned before the next imaging session to attempt to remove the small recontamination. \header ENTRY_TIME = 2003 JAN 11 01:58:09 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2002 OCT 09 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text The camera CCD was brought above freezing for 60 hours and then allowed to cool back to normal operating temperature immediately before the next imaging studies. This session consisted of 20 pattern matching and windowing tests, ten each at 47.8 and 64.0 degrees scan mirror settings, each of four 41x41 windows, and one full frame image at 15 degrees on the scan mirror to study the effect of a split field (partially on and partially off the periscope). Half of the 47.8 degree and all of the 64.0 degree tests were successful in that the pattern matching locked up, but the target stars still were not well centered. These were engineering tests and led to significant improvement in the software and to better understanding of spacecraft capabilities, but there were few data available to attempt any sort of photometric calibration following the fourth camera heating a few days earlier. The split image indicated that it should be possible to use the periscope as always intended, but that good geometric calibration will be needed, and such is being planned following the Annefrank encounter. (It is planned to do the Annefrank encounter without the periscope, starting with the S/C skewed and the mirror at 20 degrees.) One or two small images may provide some post-encounter calibration of the Annefrank images. A somewhat better level of photometric calibration is planned before and after the Wild 2 encounter. \header ENTRY_TIME = 2003 JAN 13 17:58:29 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2002 OCT 31 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text One of the goals of the engineering readiness tests on Annefrank was to exercise the optical navigation team and to attempt to improve flyby accuracy using optical data. The approach to Annefrank was from a phase angle of 150 degrees, unfortunately, which meant the asteroid would be poorly illuminated and be very faint. We had no asteroid data at phase angles beyond 100 degrees, so we weren't sure just how faint. Assuming it would be about 1 1/2 magnitudes fainter than the nearly linear decrease of about 0.03 magnitudes per degree that applies to most asteroids at smaller phase angles, we felt we would have a fair chance of detection 38 hours before closest approach. Five images were obtained using three 151x151 pixel windows and exposures of 1, 1, 2, 5, & 5 seconds. As we were to find out later, the asteroid was much fainter than expected and the spacecraft drift during the exposure (smear rate) much larger than we had previously experienced. Further, the camera pointing was not as accurate as we had expected. The use of a new controller, inadequate settle time after attitude changes, and a larger moment of inertia with the grid open were all suggested as reasons for the drift and pointing problems. The cause is still being investigated. This is why the tests were run, to make sure something like this doesn't happen to us on Wild 2. The bottom line is that the asteroid was not found in these five E-38 hour images. \header ENTRY_TIME = 2003 JAN 13 18:04:36 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2002 OCT 31 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text A second set of approach images was acquired at E-32hours. The same windows and exposure times were used as for the previous set at E-38hours. The problems were much the same, as were the results. The asteroid was not found. \header ENTRY_TIME = 2003 JAN 13 18:11:23 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2002 OCT 31 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text A third set of approach images was acquired at E-26hours. The same windows and exposure times were used as for the previous sets at E-38hours and E-32hours. The problems were much the same, as were the results. The asteroid was not found. \header ENTRY_TIME = 2003 JAN 13 18:21:26 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2002 NOV 01 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text Given the experience of the first three sets of approach images, the navigators decided to increase the window size to 181x181 pixels and make all of the exposures 5 seconds for an image set taken at E-18hours. The image smear can only be described as horrendous. This doesn't matter for measurement purposes, IF the target can be found. The asteroid was still several magnitudes too faint for detection when smeared over some 20 pixels, and it was not located. \header ENTRY_TIME = 2003 JAN 13 18:35:40 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2002 NOV 01 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text A final set of approach images was attempted at E-12hours. This time all of the available communication bandwidth was given to one window in one image, making it 701x701 pixels. The other four images were given 3x3 pixel windows and were retained only to avoid having to reprogram and transmit too much last minute command software. The smear was still large (21.7 pixels)and the asteroid still was not located. \header ENTRY_TIME = 2003 JAN 13 19:37:37 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2002 NOV 01 00:00:00 STOP_TIME = NULL TARGET = OTHER DAY = NULL \text Twenty-five minutes before the closest approach we began to acquire images to attempt autotracking. The pointing was based upon radio navigation of the spacecraft and the best ephemeris available for the asteroid. By this time the phase angle was down to 130 degrees and the range was only 11,415 km. Annefrank appeared in the first image, though far from centered. The navigators chose an exposure of 65ms to make sure they were going "deep enough," so the images were well exposed. After the first few images, only every third image was transmitted to the ground, the others being used only to initiate autotrack. After 15 minutes, at a range of 5434 km, exposure was reduced to 25 ms. In all,15 of 37 images taken with 65 ms exposures (images 371 through 407)were transmitted to the ground. Of these, the first two or three were partially on the periscope and three showed a large amount of smear, but several are of scientific use. Autotracking was initiated shortly before reducing the exposure, and image 410 and all subsequent Annefrank images are well centered in the frame. \header ENTRY_TIME = 2003 JAN 13 19:49:06 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2002 NOV 01 00:00:00 STOP_TIME = NULL TARGET = OTHER DAY = NULL \text Exposure time on Annefrank was reduced to 25 ms beginning with image 410 at a range of 5088 km and a phase angle of 113 degrees. Images beginning with #420 started to show saturation. This was predicted, but these images were being taken to test the autotracking rather than for scientific purposes, and autotrack works perfectly well with saturated images. The images soon reached 80% saturation, so images 420 through 445 are of limited scientific use. Every image was transmitted to the ground beginning with #426, a total of 26 images with 25 ms exposure. Twenty-two of these have some to nearly total saturation. \header ENTRY_TIME = 2003 JAN 13 19:58:26 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2002 NOV 01 00:00:00 STOP_TIME = NULL TARGET = OTHER DAY = NULL \text Beginning with image 446 exposure time was reduced to 5 ms. In fact the characteristics of the shutter are such that alternate images are given exposures shorter by 1.5 ms, so in fact all even numbered images have an exposure of 3.5 ms and odd numbered ones 5 ms. It was intended that these images be of scientific as well as engineering use. If Annefrank had not been acquired by this time, there was little hope of acquiring it, so there was no need to saturate the images. The subsequent 31 images (through image 476), taken at phase angles from 71.0 to 47.2 degrees constitute the best images for scientific use. During this period the range fell from 3133 km to 3078.5 km and increased back to 3162 km.