PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 80 SPACECRAFT_NAME = "CLEMENTINE 1" TARGET_NAME = {EARTH, MOON, SKY} OBJECT = TEXT INTERCHANGE_FORMAT = ASCII PUBLICATION_DATE = 1994-10-1 NOTE = "TIMELINES FOR CLEMENTINE SPACECRAFT" END_OBJECT = TEXT END CLEMENTINE ORBIT TIMELINES The Clementine orbit timeline information was added as part of the volume series just when production began. Because of the late addition of the files in this directory, they do not conform to PDS standards. Because these files are supplemental to the overall requirements of the volume design, it was decided that PDS requirements were not needed for these files. The timeline data, provided in a PDS compliant format, will be made available through the SPICE system on the Clementine ancillary data CD-ROM series. The actual spacecraft timelines are included for each of the orbits contained in this CD. They are in Microsoft Excel for Windows format. The general form of the file name scheme is as follows: TLLUNxxx.XLS - Lunar orbit timeline for revolution 'xxx' TLEPAxxx.XLS - Earth phasing loop A timeline for dump 'xxx' TLEPBxxx.XLS - Earth phasing loop B timeline for dump 'xxx' TLLEOxxx.XLS - Low Earth Orbit timeline for dump 'xxx' These timelines are based on the predicted timelines that were used to write the spacecraft command sequence scripts that were uploaded to the spacecraft for each orbit. Those predicted timelines were updated with the definitive trajectory of the spacecraft as determined by post-flight orbit determination. The timelines were then compared with the actual command scripts and console logs to ensure that they show what really happened instead of what was planned. The image summaries for the orbit were used to determine when images (during the orbit) were being taken for each camera and whether or not they were compressed, uncompressed, color, etc. It should be noted that although care was taken in developing these timelines for the CDs, some errors and omissions have occurred, partly because of incomplete or contradictory records. The timeline is a listing of significant events (orbital, spacecraft, and ground station) during the orbit as a function of time. It should be noted that the Clementine lunar orbits are numbered by convenience and not according to standard orbital dynamics practice. According to standard practice, especially with Earth-orbiting satellites, the orbit number increments when the satellite passes the ascending node. On the Clementine mission, due to the South to North polar mapping orbit, the ascending node occurred at the equator on the sunlit side of the Moon, right in the middle of mapping. This means that following standard practice, either the contiguous set of mapping images (or swath) would have to be split up between two orbits, which was unacceptable to the Clementine team, or the archived data would have to reflect both orbit numbers, e.g., Orbit 1/2. Initially this latter method was used. However, due to simplicity and convenience, the second orbit number was soon dropped and each orbit timeline and data are numbered by the orbit number at the time that mapping started, as the spacecraft crossed the South Pole. This also corresponded with the design of the timelines, because the break point for starting and ending each timeline naturally occurred during the long data dump period of the orbit, where there were usually no command scripts active. The timelines were thus designed to start and stop at aposelene (apoapsis), which is a fixed orbital point in the middle of the data dump period. It is from this point that the "Orbital Time" shown in the timelines is calculated. The timelines use the terms "periselene" for the periapsis of the elliptical lunar orbit, and "aposelene" for the apoapsis of the elliptical lunar orbit. These points in a lunar orbit are also sometimes referred to as the "perilune" and "apolune" respectively. For definitions of the acronyms and terms used in the timelines, please refer to the ancillary CD.