\header ENTRY_TIME = 2001 JUN 07 18:14:44 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 JAN 05 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text On January 5 five images were taken, a calibration lamp image and four random star fields, random because the navigators quite reasonably did not want the spacecraft moved until after EGA. The cal lamp image showed the lamp filament for the first time since the camera left the calibration lab. The four star fields now showed stars down to 9th magnitude. The point spread of the images was tremendously improved, showing near theoretical resolution. There was still a substantial skirt of scattered light present at very low dn level, but the images were tremendously improved, and this experimenter became optimistic for the first time that useful images could be acquired of the Wild 2 nucleus. \header ENTRY_TIME = 2001 JUN 07 19:09:43 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 JAN 16 00:00:00 STOP_TIME = NULL TARGET = MOON DAY = NULL \text Immediately following EGA (by ~16 hours)we acquired 25 images, 5 lunar and 2 bias frames uncompressed and 16 lunar and 2 bias frames compressed. The moon was then at a distance of 100,000 km from the spacecraft. We flew nearly over the lunar north pole of a half illuminated Moon, seeing about two-thirds "front" side and one-third "back" side. The primary purpose of the images was to photometrically calibrate the now relatively clean camera as far as possible. Images taken through the two wide band filters (OpNav and HiRes)were partially saturated as expected, since our shortest exposure time is 5 ms. Images taken through the narrow band filters were well exposed. All images exhibited a halo of scattered light around the Moon as expected from the remaining contamination. The resolution of the uncompressed images is better than the compressed ones, also as expected, since the compression chip compresses 11 to 15 dn into 1 dn, depending upon the light level of the image. \header ENTRY_TIME = 2001 JUN 07 19:45:28 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 FEB 26 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text A series of 21 compressed images was taken of star fields with the scan mirror stepped from 0 deg. to 180 deg. in 10 deg. steps. All were taken through the OpNav filter except for two additional HiRes images with the mirror at 90 deg. The purpose of these images was geometric calibration of the scan mirror, except the two HiRes images were taken once again to compare image quality of the two wide band filters. It immediately became obvious that some recontamin- ation of the optical system had occured. The point spread at the half amplitude point apparently was affected, as was the scattering skirt, but quantitative assessment was difficult since these were compressed images, with which we had little experience. It appeared that the contamination was similar to that of the previous October. Further, at the conclusion of this sequence, an EVR was received indicating that the filter wheel was still in the OpNav position rather than having returned to the C2 position as commanded. \header ENTRY_TIME = 2001 JUN 07 20:42:25 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 MAR 01 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text Three uncompressed images were taken to verify the position of the navcam filter wheel and to check the recontamination of the camera with uncompressed images. The first was a calibration lamp image, which showed that we were indeed in the OpNav position, since we had a well developed image with a 10 ms exposure. This image also showed that we were heavily recontaminated, since the filament had disappeared once again. The two star fields confirmed both of these conclusions. \header ENTRY_TIME = 2001 JUN 07 21:41:15 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 MAR 13 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text A series of images had already been planned to check the condition of the periscope and the mirror angle at which we leave the periscope. These would also check the geometric calibration through the periscope. The first magnitude star Spica (V=1.03) was used for the 0 deg and 30 deg images. Images taken at 5 deg, 10 deg, 15 deg, and 20 deg were taken without moving the space- craft and were therefore of random star fields. The periscope should transmit about 80% as much light as images taken without using it. In fact the trans- mission was about 40%, so there is some contamination of the two periscope mirrors. The point spread, as measured with images of Spica, was about the same as without the periscope. Each frame showed only one star, so no geometric calibration was possible. The periscope images also showed a great deal of scattered light with the spacecraft in its then attitude relative to the Sun. We guess that much of this came from the launch adaptor ring. We hope this will not happen with the solar panels nearly normal to the Sun as in the encounter geometry. \header ENTRY_TIME = 2001 JUN 07 22:17:14 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 MAR 22 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text At this point in time we were not sure just what had happened to the navcam, beyond the fact that it was recontaminated back to the state it had been in the previous October. Had there been recondensation of the same material we had removed or had new material condensed on the optics? Had this been occuring ever since we stopped heating or had it perhaps occurred just near perihelion when the spacecraft was the warmest it had ever been by a few degrees? The decision was made to reheat the optics, including Sun on the radiator which had been required to do any significant clean up earlier. A cal lamp image and one star field image were taken on this date to serve as a baseline for the new heating cycle. Immediately after the images were taken, the CCD heater was turned on. The scan mirror heater mechanism heater was also turned up, just as it had been for the earlier cycle, although this contributes very little energy to the area of the CCD, which is thermally isolated from the bulk of the camera. The CCD reached +12 C in about five hours. \header ENTRY_TIME = 2001 JUN 07 22:32:16 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 MAR 27 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text On March 27 another pair of images, cal lamp plus star field, were taken just before turning the spacecraft so the CCD radiator would face the Sun. The camera was still at +12 C. Forty-five minutes late another pair was taken with the camera at +21 C. A final pair was taken 12 hours later, with the camera back at +12 C. To our surprise the very first image, taken before the Sun had been turned on the radiator, was very clean, though noisy because of the high CCD temperature. In fact we could see no significant differences among the three images, before, during, and after the solar heating. Clearly this cleanup was somehow very different from the earlier ones, and it appeared to be better. \header ENTRY_TIME = 2001 JUN 07 22:46:36 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 APR 02 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text This time the decision was made to leave the CCD heater turned on for several weeks in an attempt to prevent recondensation, if that were what was happening. Further, we would take image pairs, cal lamp plus star field, every week in order to check on any changes. These April 2 images were the first such pair. Further such pairs would be taken on April 10, April 18, and April 25. As the spacecraft flew farther from the Sun, it gradually cooled, and by April 25 the CCD temperature was down to +8 C. With some concern for power supply lifetime, and with no change having been observed in the images since the heat was turned on, the heaters were turned off on April 29, having been on continuously since March 22. \header ENTRY_TIME = 2001 JUN 07 23:00:01 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 APR 30 00:00:00 STOP_TIME = NULL TARGET = OTHER DAY = NULL \text On April 30 we began a weekly series of image pairs, cal lamp plus star field, to look for any redeposition of material on the optics. With the temperature back down to a normal operating range of -36 C, we also wanted a good test of just how successful the cleanup had been. In fact the optics proved to be in their best state since launch. We were now reaching about V=10.0 in one second, without any special image processing beyond a simple stretch. To this Co-I the second contamination seems to have been very different from the first. It cleaned up rapidly at a lower temperature. My personal guess, non-verifiable of course, is that there was a recontamination near perihelion, perhaps by something as simple as water frost. I made a bet that contamination would not reappear before the next perihelion passage in 2003, if then. Meanwhile, in the short term, we will check for recondensation each week with a pair of images. \header ENTRY_TIME = 2001 JUN 07 23:11:55 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 MAY 31 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text Recontamination checks were made on May 7, May 17, May 25, and May 31. One was planned for June 4, but there was a transmitter problem at the Madrid DSN site. There is no evidence in any of these four images of any change from that of April 30 or in fact from the high temperature images of March 27 and after. The spacecraft is now far enough from Earth that transmission rates are dropping. A study of the encounter guide star field and scattered light with the spacecraft in the attitude of the encounter is planned for June 8 with Earth return on June 14. A final recontamination check is planned for July 3. There will be only an occasional check (every six months?) of camera health for the next 18 months after July 3. \header ENTRY_TIME = 2001 AUG 15 21:28:25 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 JUN 08 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text A series of 16 images was planned for geometric calibration, to check scattered light with the S/C in the encounter attitude relative to the Sun and almost at the encounter distance, and to image the actual encounter field. All images taken through the periscope show considerable scattered light, presumably from the launch adaptor ring, and significant contamination. The brighter stars near the field center seem adequate for autoguidance, however. Images taken at 20 and 30 degree mirror angles were excellent, free of all scattered light. A five second exposure of the encounter field at 30 degrees mirror angle showed stars to magnitude 11.7 with a signal to noise of three. Images at larger angles were not perfect due to mirror motion (not quite enough time was allowed between motion and exposure), but they probably still are adequate for geometric calibration of the mirror. Images planned for July 3 as a final recontamination check were not taken at that time but are now planned for August 29, a full four months after all heating ceased. \header ENTRY_TIME = 2003 JAN 10 22:51:50 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 JUN 08 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text Sixteen full frame uncompressed images were taken of the Wild 2 encounter back- ground field with exposures of one, three, and five seconds, at various scan mirror settings, and with the spacecraft in encounter attitude for periscope images, to check for scattered light. With a 0 degree mirror angle there was about 200 dn/s of scattered light in the upper left corner, the worst part of the frame. With a 10 degree mirror angle, there was about 100 dn/s of scattered light in the upper left corner. At 20 degrees, and clear of the periscope, there was no scattered light detected. Processing of a five second exposure clear of the periscope indicated we reached magnitude 11.7 with a signal to noise ratio of three. There has been no further evidence of contamination since the third heating cycle began on March 22. These are images 282-297. \header ENTRY_TIME = 2001 SEP 14 21:52:59 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 AUG 29 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text Two images (#s 298 & 299)were acquired to check for any recontamination of the camera and to furnish additional geometric calibrations. Both proved excellent, showing no new contamination for the past four months. No additional imaging is planned until the windowing software patch is available or until standard "maintenance" requires a camera status check (in about six months). Useful unwindowed imaging will not be possible for a year or more, that is, until we have more power and a higher data rate as we begin to approach Sun and Earth once again. \header ENTRY_TIME = 2003 JAN 10 22:30:21 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 AUG 29 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text Images #298 and #299 were taken as a final check on possible recontamination and to furnish additional geometric calibration, in view of the loss of several images from the previous run. Both images proved excellent, showing no new contamination during the previous four months. No additional imaging is planned until windowing software is available, since both power and communication rate continue to decrease as we move farther from the Sun and Earth. \header ENTRY_TIME = 2003 JAN 10 23:04:50 SYSTEM_NAME = NAVCAM AUTHOR = RAY L. NEWBURN, JR. INSTITUTION = JPL (CHIPTON-ROSS) START_TIME = 2001 OCT 29 00:00:00 STOP_TIME = NULL TARGET = STAR DAY = NULL \text As it became more and more clear that a true engineering readiness test for Wild 2 was only possible by using the asteroid Annefrank, it became of great importance to determine whether there might be a scattered light problem on the approach vector to Annefrank, given our very large 150 degree phase angle. It was therefore decided to take one full frame uncompressed image, at the 20 degree mirror angle planned for the approach, with the spacecraft in the approach attitude relative to the Sun. There was no scattered light problem, and there was no evidence of any recontamination.