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STARDUST NAVCAM IMAGES OF WILD 2 - VERSION 2.0 (PDS)

NSSDCA ID: PSSB-00185

Availability: Archived at NSSDC, accessible from elsewhere

Description

This description was generated automatically using input from the Planetary Data System. Data Set Overview ================= This data set contains raw pre-encounter and encounter images taken by the Stardust Navigation Camera during the encounter with comet Wild 2. This is version 2.0 of the dataset, in which the IMG formatted images have been converted to FITS format, and a number of corrections, described below, have been applied. This version supersedes version 1.0. Every image provided in this data set was taken as a part of a particular imaging sequence, each of which is described in this section by the NAVCAM Science Lead, Dr. Raymond L. Newburn, Jr. For the complete list of images and their parameters, refer to the data set's index table, INDEX/INDEX.TAB. For additional notes on individual images also consult with the document ``Log of Stardust NAVCAM Flight Images'', DOCUMENT/PIIMGLOG.PDF, provided with this data set. 2003 JAN 28 12:33:36 -- Images 477-509 -------------------------------------The primary purpose of images 477 through 507 was geometric calibration of images taken through the periscope. Images 508 and 509 were tests of windowing, using a 151 x 151 window. Photometric calibration of these was a secondary goal. The target for all images was the Pleiades (M45, an open cluster). For the primary purpose, the scan mirror was set at one degree intervals from 0 through 20 degrees. All images showed a significant amount of scattered light, but they still were useful for geometric calibration of images taken through the periscope. The images showed significant doubling with part of the light coming through the periscope and part of it around the periscope, the two images separated by about 17 pixels. None of the images were of significant use for photometric calibration. 2003 MAY 21 21:09:43 -- Images 510-513 -------------------------------------After almost four months since the last image, this series of four images (510-513) was intended as a check of the camera and the state of its optical system. Image 510, taken through the periscope, seemed to indicate severe contamination, both of the periscope and the rest of the optical system. Image 511, taken of the calibration lamp showed the lamp filament plainly but also showed a very mottled background. This showed that there was contamination of both the periscope and the camera optics. The final images, off the periscope, seemed to indicate that the camera was in better shape than the periscope. Clearly, another heating cycle was needed to clean up the camera. 2003 OCT 08 22:11:21 -- Images 514-517 -------------------------------------Much of the contamination seen in the images 4 1/2 months earlier was on the periscope, which could not be heated without turning the Sun on the battery immediately above it. This is not permitted by spacecraft flight rules. We could, however, turn the Sun on the camera radiator once again, if necessary. Images 514 through 517 were an additional check on the state of the camera, and the camera was found to be heavily contaminated. The first image, of the calibration lamp, showed it to be in much worse shape than it had been the previous May. The other three images, of a star field and off the periscope, were virtually blank, even with a five second exposure for two of them. 2003 OCT 11 23:06:37 -- Images 518-521 -------------------------------------On October 11 the previous cycle of images was repeated as numbers 518 through 521. A few stars in the two 5 second exposures indicated that the contamination was now ``only'' about 2 1/2 magnitudes (a factor of 10)! Just turning on the CCD heater prior to this data set had helped, but not nearly as much as needed, so commands were sent to put the Sun on the CCD radiator once again. 2003 OCT 30 15:07:34 -- Images 522-525 -------------------------------------Following a full heating with the Sun on the radiator and the CCD and scan mechanism heaters turned on, this set of four image (522 through 525) was meant to determine how successful we had been in clearing off the contamination adhering to camera components. We found that contamination had been reduced from 2.5 magnitudes to about 0.5 magnitudes (a factor of ten to a factor of 1.58 reduction in transmission). These much improved images utilized exposures of one second, five seconds, five seconds, and finally 20 milliseconds with the calibration lamp turned on. For some reason, the calibration lamp didn't seem to have been turned on. (This happened again just before the Wild 2 encounter. It may have been caused by solar particle radiation flipping a bit somewhere in the lamp or shutter logic circuits.) 2003 NOV 08 16:15:03 -- Images 526-527 -------------------------------------Images 526 and 527 were intended as shutter checks, because the calibration lamp hadn't appeared in image 525. Image 526 was a five second timed exposure on a star field. It appeared perfectly normal. Image 527 tested the bulb mode, where the shutter is commanded open and stays open until it receives the close command. This method also worked perfectly. The lack of an image of the calibration lamp in image 525 remains an enigma. 2003 NOV 13 06:56:05 -- Images 528-530 -------------------------------------Images 528, 529, and 530 were 3 second full frames exposed on the encounter field. We were concerned about the number of background stars available for optical navigation, this not being the richest field in the sky. We also wanted to check, once again, how much scattered light might confront us. As we expected, there were no severe problems with scan mirror settings of less then 170 degrees. Since these images were of the encounter field, chief optical navigator Shyam Bhaskaran scanned a frame looking for Wild 2. There seemed to be something at about the correct position. He co-added the three frames and was convinced he had found Wild 2. Others present at his request were even more sure that he had found the comet. These were the first images taken to search for Wild 2, and the project heaved a huge sigh of collective relief at the comet having been located in nearly the predicted place more than six weeks before the encounter. 2003 NOV 17 16:59:59 -- Images 531-555 -------------------------------------Images 531 through 555 were a test of windowing and pattern matching. All images in this group used four 51 x 51 pixel windows, three on stars and one on the expected position of Wild 2. Image 532, if it ever existed, was not transmitted to the ground. The proper windows were created in every case, but the pattern matching varied from no match, to matched with stars near the edge of the window to stars nearly centered. All were taken with exposures of 5 seconds (531 through 550) or 15 seconds (551 through 555). Individually, none provided an obvious image of Wild 2. 2003 NOV 20 17:00:00 -- Images 556-558 -------------------------------------This was a set of three full frame images. The first of them, 556, was missing some packets and was a bit of a mess. The other two were fine 5 second and 15 images and served to confirm quite definitely the presence and location of Wild 2. Needless to say, having definitely acquired the location of Wild 2 this early was a huge relief to the STARDUST team. 2003 NOV 24 04:00:00 -- Images 559-583 -------------------------------------Images 559 through 583 were windowed images, in this case three 51 x 51 images and one 71 x 71 image, the latter the window on the predicted comet position. Twenty of these were 5 second exposures and five were 15 second exposures. Eight images were not pattern matched, while the other 17 seemed to work perfectly. The image of Wild 2 can be seen in each individual 71 x 71 image, that is properly locked, by using a bit of stretch. 2003 NOV 27 17:00:00 -- Images 584-608 -------------------------------------Images 584 through 608 were a repeat of the previous set, except they were divided into 10 at five second exposures and 15 at fifteen second exposures. The same window sizes were used, 51 x 51 for the stars and 71 x 71 for the comet. This time only five did not lock up (pattern match). These images were intended for optical navigation, as was the previous set. 2003 DEC 01 05:00:24 -- Images 609-633 -------------------------------------Images 609 through 633 were intended to be another set of 25 optical navigation images using three 51 x 51 pixel images and one 71 x 71 pixel image. Only four of them achieved pattern matching, however, and those were very poorly centered. These were of little use. 2003 DEC 04 10:44:18 -- Images 634-673 -------------------------------------Images 634 through 673 were periscope checks, intended to see how well the spacecraft could be guided when it had to be pointed in the ram direction. The first nine frames were full frame 5 second exposures at a scan mirror angle of 1.94 degrees. All exhibited considerable scattered light. The next four images were again full frame, but this time at a scan mirror angle of 1.57 degrees. The exposures were 15, 7.5, 5, and 3 seconds. Again there was a great deal of scattered light. The remainder of the frames were taken at a mirror angle of 16.82 degrees. The first two of these were again full frames using a 15 second exposure. The remainder were all windowed, using three 51 x 51 pixel sizes and one using 71 x 71 pixels. They utilized exposures of 5 seconds or 15 seconds. All of these contained a great deal of scattered light, and none were successful in pattern matching. 2003 DEC 08 13:00:00 -- Images 674-698 -------------------------------------The next set of 25 images, 674 through 698, were taken off periscope at a scan mirror angle of 34.24 degrees. All were windowed with three windows 51 x 51 pixels and one window 71 x 71 pixels. The first five images had five second exposures, the next five had 10 second exposures, and the final 15 used 15 second exposures. The first five images did not achieve lock, nor did the last of the 10 second exposures. The first four 10 second exposures and all of the 15 second exposures achieved a good lock. 2003 DEC 09 05:00:00 -- Images 699-724 -------------------------------------This set of 25 images (699 through 724) was taken strictly for optical navigation purposes. The first five received an exposure of 5 seconds, the second five 10 seconds, and the third, a group of 15, received an exposure of 15 seconds. Pattern matching was not achieved on the first five (699-703), nor on 705, 706, 708, 710, 714, 716, 718, 722, or 723. Image 724 which is a full frame, shows considerable scattered light as well as a strange artifact of several adjacent columns. This artifact also appears in the other images of this group, but fortunately it does not cross any of the windows. Looking back, the artifact apparently first appeared in image 701. All of this still left 11 good images for optical navigation purposes. P/Wild 2 still is an easy target in the 71 x 71 window of each image. 2003 DEC 10 05:00:00 -- Images 725-749 -------------------------------------This set of 25 images (725 through 749) again was taken strictly for optical navigation purposes. The first five received an exposure of 5 seconds, the second five 10 seconds, and the third, a group of 15, received an exposure of 15 seconds. Pattern matching was achieved on only four windows, 730, 732, 734, and 738. The artifact, first seen in image 701, is apparent in this set of images as well. 2003 DEC 11 05:00:00 -- Images 750-774 -------------------------------------This set of 25 images (750 through 774) again was taken strictly for optical navigation purposes. The first five received an exposure of 5 seconds, the second five 10 seconds, and the third, a group of 15, received an exposure of 15 seconds. Pattern matching was achieved on only five images, 755 through 759. The artifact, first seen in image 701, is apparent in this set of images as well, but seems to be fading. 2003 DEC 12 11:59:59 -- Images 775-800 -------------------------------------This set of images, 775 to 800, was another set taken just like previous sets except the scan mirror was set at an angle of 31.84 degrees. Again exposures were set at 5 seconds for the first five, 10 seconds for the second five, and 15 seconds for the final fifteen. The first fourteen of the 15 second exposures were windowed, three at 51 x 51 pixels and one at 71 x 71 pixels. The last image was a full frame. The pattern was not matched on ANY of the windowed images. So we were left with only one image, number 800, and that had severe scattered light problems. 2003 DEC 13 05:59:59 -- Images 801-825 -------------------------------------This set of images, 801 to 825, was another set taken just like previous sets except the scan mirror was set at an angle of 31.43 degrees and the final image was also windowed. Again exposures were set at 5 seconds for the first five, 10 seconds for the second five, and 15 seconds for the final fifteen. All 25 exposures were windowed, three windows at 51 x 51 pixels and one at 71 x 71 pixels. The pattern was not matched on any of the first 24 images. So we were left with only one properly pattern matched image, number 825, which showed the comet quite clearly. 2003 DEC 14 12:00:00 -- Images 826-850 -------------------------------------This set of images, 826 to 850, was another set taken just like earlier sets, except the scan mirror was set at an angle of 30.63 degrees and the final image again was windowed. Again exposures were set at 5 seconds for the first five, 10 seconds for the second five, and 15 seconds for the final fifteen. All 25 exposures were windowed, three windows at 51 x 51 pixels and one at 71 x 71 pixels. One image, 835, was missing many packets. Two windows were missing entirely and the third was only partially present. The pattern was matched on only five images, 831, 833, 839, 847, and 850. 2003 DEC 15 12:00:00 -- Images 851-853 -------------------------------------Realizing the poor yield of the pattern matching program with small windows, it was decided to use fewer but much larger windows, 201 x 201, and not to attempt pattern matching. Image 851 utilized three of these much larger windows. Image 852 used two 201 x 201 windows and one 1 x 1 image, which significantly reduced the amount of data to be returned. Image 853 once again used three 201 x 210 windows. All were 15 second exposures at 30.69 degrees scan mirror setting, and all showed the comet. 2003 DEC 16 05:00:00 -- Images 854-856 -------------------------------------The December 16 set of Op Nav images was composed of three 201 x 201 pixel windows, 854, 855, and 856. These were all 15 second exposures at a scan mirror angle of 30.29 degrees. The only significant problem was that the bad columns, that first appeared in image 701, fell right across two of the windows, which were set a bit too far to the right in the frame. 2003 DEC 17 05:00:00 -- Images 857-859 -------------------------------------The December 17 set of Op Nav images was composed once again of two 201 x 201 pixel windows and one 1 x 1 pixel window. These are numbered as windows 857, 858, and 859. All were 15 second exposures at a scan mirror angle of 29.65 degrees. All were properly placed, with the bad columns now falling between windows. 2003 DEC 18 04:00:00 -- Images 860-876 -------------------------------------The sequence of December 18 was meant to serve two purposes. The first 14 full frame uncompressed images were meant to photometrically calibrate the camera for the encounter, now only two weeks off. Images 860 and 873 are bias frames. Images 861 through 869 were off periscope images taken at a scan mirror setting of 23.98 degrees. Images 870, 871, and 872 included the periscope in the light path with the scan mirror set at 0.20 degrees. The final three frames, 874, 875, and 876 were meant to further understand periscope use when it included light both through the periscope and around it. The sad thing is that none of these images were of significant use. All contained many thousands of hot pixels as well as a generally high background level. The camera electronics had been left turned on to prevent possible failure due to excessive on and off cycles, the time when most electronics fail, if they are going to do so. Hereafter the electronics were turned off when not in use, and everything worked just fine. There was now no time for an additional photometric calibration before encounter, so it was decided to go with just the planned post-encounter photometric calibration. 2003 DEC 19 12:00:00 -- Images 877-879 -------------------------------------Images 877 through 879 were once again for optical navigation. These images all used 15 second exposures with the scan mirror set at 28.40 degrees. Wild 2 was now quite easy to see on each individual frame. 2003 DEC 20 12:00:00 -- Images 880-882 -------------------------------------Images 880 through 882 were once again for optical navigation. These images all used 15 second exposures with the scan mirror set at 27.88 degrees. Wild 2 was now quite easy to see on each individual frame. 2003 DEC 21 11:59:59 -- Images 883-885 -------------------------------------Images 883 through 885 were once again for optical navigation. These images all used 15 second exposures with the scan mirror set at 27.25 degrees. Wild 2 is now quite easy to see on each individual frame. 2003 DEC 22 03:59:59 -- Images 886-889 -------------------------------------Images 886, 887, and 888 were again for optical navigation. Image 889 does not exist for unknown reasons. These images all used 15 second exposures with the scan mirror set at 26.96 degrees. All continued to use three 201 x 201 pixel windowing. 2003 DEC 24 03:00:44 -- Images 890-906 -------------------------------------Images 890 through 906 were still taken for optical navigation. All images were taken with a 20 second exposure at a scan mirror angle of 24.10 degrees. All consist of three windows, now 301 x 301 pixels in size. 2003 DEC 25 02:00:44 -- Images 907-924 -------------------------------------Images 907 through 924 were still taken for optical navigation. All images were taken with a 20 second exposure at a scan mirror angle of 24.10 degrees. All were meant to consist of three windows, again 301 x 301 pixels in size. Image 907 does not exist. Images 908, 909, and 910 are all incomplete, consisting in each case of a single incomplete window. The remainder of the images are very good normal frames. Since new data were being taken every day, no attempt was made to retransmit the incomplete images. 2003 DEC 26 03:00:45 -- Images 925-942 -------------------------------------Images 925 through 942 were still taken for optical navigation. All images were taken with a 20 second exposure at a scan mirror angle of 23.57 degrees. All were meant to consist of three windows, again 301 x 301 pixels in size. Image 925 does not exist. Images 927 through 930 are also missing for unknown reasons. The remainder, 931 through 942 are excellent. Again no attempt was made to retransmit the missing images, if in fact they ever existed. So many images were being taken that it was pretty easy to lose track of which had and which had not been taken. It was always much safer to skip a few numbers than to give two images the same number. 2003 DEC 26 16:00:00 -- Images 943-960 -------------------------------------This set of images made up the second optical navigation sequence of December 26, as optical navigation prepared for the final TCMs, if they proved necessary. They are images 943 through 960, consisting of 20 second exposures at a scan mirror angle of 23.30 degrees. Each consisted of three 301 x 301 windows. All turned out quite well. 2003 DEC 28 02:01:30 -- Images 961-978 -------------------------------------Following a day ``off'' when an additional heating cycle was carried out for a decontamination of the camera, optical navigation images were resumed, images which also determined the then current state of the camera. Images 961 and 962 appear not to exist. Image 963 appears to consist of one window with many missing packets. Images 964 and 965 have single partial windows, each with many missing packets. Image 967 consists of two windows, only one of which is complete, but the complete window does contain a usable image of the comet. Images 966 and 968 through 978 have the normal three windows of 301 x 301 pixels. Three of these have 20 second exposures and nine were given 10 second exposures. All were taken with the scan mirror at 22.49 degrees. 2003 DEC 29 05:00:00 -- Images 979-996 -------------------------------------In the series of images 979 through 996, only 983 and 984 are missing packets. All images were acquired at a scan mirror angle of 21.87 degrees. Images 979 through 982 and 985 through 987 were given 20 second exposures, while 988 through 996 received 10 second exposures. All complete images had three 301 x 301 pixel windows. 2003 DEC 30 05:27:15 -- Images 997-1014 --------------------------------------Images 997 through 999 were missing the first packet, thereby ruining each entire image. In this hectic period, no attempt was made to reconstruct them. Image 1000 consisted of one normal 301 x 301 pixel window and two 1 x 1 pixel windows. The image of Wild2 was in one of the latter. Images 1001 through 1014 were normal, each having three 301 x 301 windows. The first five good frames received 20 second exposures, and the last nine were all 10 second exposures. These, of course, were again taken for optical navigation purposes. 2003 DEC 30 22:35:15 -- Images 1015-1032 ---------------------------------------The second set of December 30 images probably included 1015 through 1021, which are missing. I say this because there are only two images with 20 second exposures instead of the usual nine. The two 20 second images are 1022 and 1023. These are followed by 1024 through 1032, which are 10 second exposures. All were taken at a scan mirror angle of 21.00 degrees and with three 301 x 301 pixel windows. 2003 DEC 31 07:00:00 -- Images 1033-1050 ---------------------------------------Images 1033 through 1050 constituted the first set of December 31 exposures. All were taken at a scan mirror angle of 20.77 degrees and with three 301 x 301 pixel windows. The first nine were 20 second exposures and the second nine were 10 second exposures. 2003 DEC 31 20:18:00 -- Images 1051-1058 ---------------------------------------The second set of December 31 images consisted of eight images numbered 1051 through 1058. The first four were 15 second exposures, the second four 10 seconds. All utilized a scan mirror of 24.49 degrees. Each consisted of three windows of 291 x 291 pixels. 2004 JAN 01 00:18:00 -- Images 1059-1066 ---------------------------------------The first set of January 1 images, 1059 through 1066, were taken at a scan mirror angle of 24.49 degrees. All were windowed images using three 291 x 291 pixels with a scan mirror angle of 24.49 degrees. The first four were 15 second exposures, the second four, 10 second exposures. 2004 JAN 01 05:18:00 -- Images 1067-1074 ---------------------------------------The second set of January 1 images, 1067 through 1074, were also taken at a scan mirror angle of 24.49 degrees. All were windowed images using three 291 x 291 pixels with a scan mirror angle of 24.49 degrees. The first four were 15 second exposures, the second four, 10 second exposures. 2004 JAN 01 08:18:00 -- Images 1075-1082 ---------------------------------------The third set of January 1 images, 1075 through 1082, once again were taken at a scan mirror angle of 24.49 degrees. All were windowed images using three 291 x 291 pixels with a scan mirror angle of 24.49 degrees. The first four were 15 second exposures, the second four, 10 second exposures. 2004 JAN 01 12:18:00 -- Images 1083-1090 ---------------------------------------The fourth set of January 1 images, 1083 through 1090, once again were taken at a scan mirror angle of 24.49 degrees. All were windowed images using three 291 x 291 pixels with a scan mirror angle of 24.49 degrees. The first four were 15 second exposures, the second four, 10 second exposures. 2004 JAN 01 16:18:00 -- Images 1091-1098 ---------------------------------------The fifth set of January 1 images, 1091 through 1098, once again were taken at a scan mirror angle of 24.49 degrees. All were windowed images using three 291 x 291 pixels with a scan mirror angle of 24.49 degrees. The first four were 15 second exposures, the second four, 10 second exposures. 2004 JAN 01 21:18:44 -- Images 1099-1106 ---------------------------------------The sixth set of January 1 images, 1099 through 1106, were taken at a scan mirror angle of 24.49 degrees. All were windowed images using three 291 x 291 pixel windows. Image 1099 was missing. Image 1100 had two windows, but only the image containing the comet was complete. Images through 1102 were 15 second exposures, the last four were 10 second exposures. 2004 JAN 02 05:18:44 -- Images 1107-1122 ---------------------------------------Images 1107 through 1115, one complete set, are missing. The final set of optical navigation images, numbered 1116 through 1122, were acquired using three 291 x 291 pixel windows and a scan mirror angle of 24.49 degrees. The first three utilized 15 second exposures and the final four 10 second exposures. 2004 JAN 02 18:54:28 -- Images 2000-2115 -- Wild 2 Encounter Set ---------------------------------------------------------------Images 2005 through 2115 are the 81P/Wild 2 encounter set. There are 72 complete images in this set, the missing numbers having been used only to establish the auto-tracking on the nucleus. There was sufficient memory only for the 72 images. It is the nature of the shutter that alternate exposures are 1.65 milliseconds shorter than the set exposure time. The even numbered images are the shorter ones taken during the encounter. We were quite limited in the number of changes that could be made in the exposure time, so most were taken at settings of either 100 milliseconds (actually 98.35 milliseconds) or 10 milliseconds. Many of the longer exposures were saturated, but these serve very well to bring out the many jets of gas and dust ejected by the comet. Scan mirror angles ranged from 1.37 degrees for image 2005 through 176.05 degrees for image 2115. The images with the mirror at more than 170 degrees all exhibit a great deal of scattered light, probably from the sample return capsule. There are lesser amounts of scattered light on images back to about 160 degrees. There is a problem with images taken near 0 degrees as well, from light scattered from the launch vehicle adapter ring which actually occludes a bit of the periscope. 2004 JAN 13 02:24:28 -- Images 2116-2130 ---------------------------------------Images 2116 through 2130 were taken to attempt to calibrate all of the images, to check the post-encounter state of the periscope, and to check the calibration lamp, which appeared to have failed pre-encounter. Images 2116 and 2129 were bias frames. Images 2117 through 2125 constituted the very limited calibration set. Images 2126 through 2128 were for the periscope check, and 2130 was the calibration lamp check. The calibration images all were taken at scan mirror angles near 24 degrees, four with 1 second exposures, four with 5 second exposures and one with a 15 second exposure. All were uncompressed full frame images. The periscope checks were done at an angle of -0.10 degrees and were full of scattered light. This was expected to some extent, but the very mottled appearance of the images indicated that one or both mirrors of the periscope were thoroughly sandblasted by the passage through the Wild 2 coma. The check of the calibration lamp unfortunately was done with a 1 second exposure rather than 20 milliseconds. It was obviously working just fine, since every pixel in the frame was saturated. Processing ========== The images in this data set were created by the DMAPKTDECOM program developed by Applied Coherent Technology Corp, Herndon, Virginia and operated by the Stardust Data Management and Archive Team at JPL, Pasadena, California. This program assembled images from raw telemetry packets sent down by the spacecraft and populated the images labels with housekeeping values, decommutated the binary image headers, and computed geometry parameters using SPICE kernels. This program did not apply correction of any kind to the image data. In the cases when only certain sections of the detector were downlinked, the program filled the pixels in the image corresponding to the areas for which data had not been downlinked with hex null values (i.e., zeroes). In such images window objects were used to define the areas containing non-null data. The images were converted from PDS format into FITS format at the PDS Small Bodies Node. For the images that originally consisted of window objects, the window data has been embedded into full-frame images, with regions that were not downlinked set to zero. During the conversion process, the overscan pixels on both sides of the images were recovered from the IMG files. (For consistency, the overscan regions were inserted into the windowed images, though their pixel values are set to zero.) Also, the orientation set up so that the images are properly oriented when displayed as defined by the LINE_DISPLAY_DIRECTION and SAMPLE_DISPLAY_DIRECTION keywords, and the twist angle was corrected to conform to the PDS definition. Data ==== The images in this data set were originally produced in standard PDS format, and then converted to FITS format. Each file includes a detached PDS label. The label also describes the circumstances surrounding the collection of the calibration image. Camera Description -----------------The camera has a 1024x1024 array as the active portion of the CCD. The images that are stored on this volume, however, contain more than just the active portion of the CCD. Each line contains a sync pattern, a line counter, 12 baseline stabilization pixels, the 1024 pixels from the active portion of the CCD, and finally 8 over-clock pixels used to measure the quantum efficiency. The number of rows for each image is always 1024, no matter what compression mode is used, but the number of columns for each image depends on the compression mode used. Compression Modes ----------------The NAVCAM images can be either 8-bit or 12-bit data. The 12-bit data is commonly referred to as 'uncompressed data', while the 8-bit is referred to as 'compressed data'. This compression is accomplished by a 12-bit to 8-bit square-root look-up-table compression method, which is implemented in the hardware of the camera electronics. This compression is lossy and the estimate of the 12-bit image can be recovered using the look-up table mentioned in Appendix 3 of the Calibration Document. Both the image and histogram portions of the data file require different amounts of storage space, dependent on the compression mode used. In uncompressed mode with 12-bit data, the pixels are expressed in two bytes, as 16 bits per pixel. The upper nibble of the most significant byte is always zero for these images. During the conversion to FITS format, all of the images were stored as 16-bit integers. A record of whether the original data were compressed or not is retained in the COMPRESSION_TYPE keyword in the PDS labels (COMPRESS in the FITS header). A value of '8_BIT' indicates the 8-bit data, and a value of 'NONE' denotes uncompressed images. Exposure Durations -----------------The double-bladed shutter utilized by the camera has a delay in its slide mechanism that introduces an offset in the actual exposure time, compared to the commanded exposure time. During the recalibration of the NAVCAM as part of the Stardust NExT mission, it was determined that the original information about the exposure time offsets and the forward/reverse shutter parity were incorrect. In this version (2.0) the images have been corrected to account for the updated information. See the file SHUTTER_CORRECTION.ASC in the documents directory for more information. Target Name in the Image Labels ------------------------------The target name in the image labels was set only for the images where the target is either seen in the image or computed to be within the camera field of view. For all other images the target name was set to ``CALIBRATION FIELD''. Consequently the label geometry items pertaining to the target -- spacecraft-target position, velocity and distance, pixel scales, and phase angle -- are only supplied for the images where target name is not ``CALIBRATION FIELD'' and were computed for that specified target. Windowed Images --------------The IMAGE size parameter in the image label reflects the size of the detector, however in some cases data from only certain sections of the detector were downlinked. In these cases the pixels in the image corresponding to the areas for which data had not been downlinked are filled with hex null values (i.e., zeroes). Noise in the Images ------------------If the images are stretched to the limit, regular wide horizontal stripes appear in every image at the level of 1 to 2 dn above background. These appear to be the product of coherent noise somewhere in the data stream or from a power supply. Their source is unknown. Ancillary Data ============== The geometry items included in the image labels were computed using the following SPICE kernels archived in the Stardust SPICE data set, SDU-C-SPICE-6-V1.0: Kernel Type File Name ------------ --------------------LSK naif0008.tls PCK pck00007.tpc PCK sdu_wild2_v01.tpc SCLK sdu_sclkscet_00141.tsc FK sdu_v20.tf IK sdu_navcam_v22.ti SPK sdu_l_2003_w2.bsp SPK sdu_l_2004.bsp SPK sdu_w2_opnav.bsp CK (s/c) sdu_sc_rec_2003_w2_v2.bc CK (s/c) sdu_sc_rec_2004_v2.bc CK (s/c) sdu_sc_rec_w2_opnav.bc CK (camera) sdu_nc_rec_v2.bc Coordinate System ================= Geometric Parameter Reference Frame ----------------------------------Earth Mean Equator and Vernal Equinox of J2000 is the inertial reference system used to specify observational geometry items provided in the image labels. Geometric parameters are based on best available SPICE data at time of image creation. Epoch of Geometric Parameters ----------------------------All geometric parameters provided in the image labels were computed at the epoch specified in the START_TIME label field. Image Orientation and Geometry -----------------------------In version 1.0 of this data set, the image orientation was was flipped from what would be seen by an actual observer. In addition, the TWIST_ANGLE that was given did not correspond to the definition in the PDS Data Dictionary. Both of these inconsistencies have been corrected in this version of the data. When displayed as defined in the SAMPLE_DISPLAY_DIRECTION and LINE_DISPLAY_DIRECTION keywords, the image would appear as it would to an in situ observer, and the TWIST_ANGLE corresponds to the definition given in the PDS Data Dictionary. Additional keywords have been added to the FITS header to better define the geometry, including the Celestial and Ecliptic North clock angles and the projected sunward vector clock angle. In this version, all geometric parameters have been recomputed using the most recent SPICE kernels (listed above) Software ======== The images in this data set are in standard FITS format and, therefore, can be viewed by any standardized FITS reader. For this reason no special software is provided with this data set. Contact Information =================== For any questions regarding the data in this archive, contact the SBN: Tony L. Farnham Phone: +1 (301) 405-3856 Electronic mail address: farnham@astro.umd.edu Department of Astronomy University of Maryland College Park, MD 20742 USA or Stardust Data Management and Archive Team (SDMA): Charles H. Acton, Jr. Phone: +1 (818) 354-3869 Electronic mail address: Charles.Acton@jpl.nasa.gov Boris V. Semenov Phone: +1 (818) 354-8136 Electronic mail address: Boris.Semenov@jpl.nasa.gov MAIL STOP 301-125L Jet Propulsion Laboratory California Institute of Technology 4800 Oak Grove Drive Pasadena, CA, 91109-8099 USA

Alternate Names

  • SDU-C-NAVCAM-2-EDR-WILD2-V2.0

Discipline

  • Planetary Science: Small Bodies

Additional Information

Spacecraft

Experiments

Questions and comments about this data collection can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Ray L. Newburn, Jr.Data ProviderNASA Jet Propulsion Laboratorynewburn@scn1.jpl.nasa.gov
Dr. Ray L. Newburn, Jr.General ContactNASA Jet Propulsion Laboratorynewburn@scn1.jpl.nasa.gov
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