PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT PUBLICATION_DATE = 2001-09-01 NOTE = "Description of the PRE_EROS_OBSV_GUIDE files in this directory." END_OBJECT = TEXT END Column Descriptions for the MSI Pre_Eros Observation Guide: The MSI Pre_Eros observation guide describes some basic information about each MSI observation that was acquired during the NEAR mission prior to 1998. An 'observation' is a convenient unit for organizing the data and refers to the process of sequencing. The observations within these guides were developed essentially by hand in STOL. This differs from the sequences after 998-210 which were built in SEQGEN. A different organizational structure was required for each which is why the mission was divided in this manner. The following fields are recorded: 1. Orbit Occasional entries in this column give range to target (tbd). This is only applicable for the Mathilde flyby and the EarthMoon Swingby. Additional range and viewing information will be available in the mathilde_orbital_info.txt and earthmoon_orbital_info.txt files, in the respective subdirectories. 2. Sub-solar Latitude - tbd, will be sub-solar latitude on the target (earth or mathilde). 3. Observation This is a unique descriptive term identifying the name of the observation. This represents a unit of sequencing which acquired a set of images. The data acquired within an observation were generally taken as a discrete event with a common purpose. 4. Year-Doy This describes the year and day of year of the start of the observation. 5. Sequence - In the Pre_Eros spreadsheet, this column will be a link to the STOL script for the sequence. Sometimes this will be preceded by a text description of the sequence. The pre_eros_seq_archive.txt has some examples which will show you how to interpret the STOL script. Please refer to the observation_overview.txt file for the names and locations of additional files available such as imagelists. 6. MET Range This is the range of METs for the observation (spacecraft mets for first and last images in the observation). 7. Start UTC This is the UTC of the first image in the observation. 8. End UTC This is the UTC of the last image in the observation. 9. Sequence ID (tbd) Up to 12 unique Sequence Definitions were resident in the MSI DPU during the Pre_Eros phases. Each of these Sequence Definitions contains a parameter, the Seq ID, which is an integer between 1 and 12, that uniquely distinguishes it from the other Seq Defs. A Sequence Definition defines the format by which images are acquired (number of images, spacing, compression, exposures, filters, etc). Seq Defs were executed by calling the Seq ID. We could redefine the parameter values in any or all of the Sequence Definitions at any time during the mission. There is currently no SeqID log available for this period as in the Eros phases. But you can go to the STOL sequence file and find where the SEQ ID has been loaded just prior to the observation. (if I have time before the final is due I'll list these out in some useful manner). A better way to get the same information is to look in the image header, where you can find listed the compression, exposure values, and so forth for that image. An imagelist (if available) is another way to get an overview of some of this information. 10. Filters This is a list of the filters that were used during this Sequence. 11. Number of Nonzero Images This is the number of images acquired by this observation which had non-zero exposure values. 12. Number of Zero Exp Images This is the number images acquired by this observation which had zero exposure values. 13. Compression This lists the type of compression used for the images acquired in this observation. (tbd) 14. Description A short description of the observation. 15. Detailed Description - In a few cases there are text files that offer more detailed information. They will be linked from the spreadsheet, or at the very least referenced by name. They will be located in the /pre_eros subdirectory. The observation_overview.txt also contains detailed descriptions of many observations. 16. Gifs - These are predict plots generated by our visualization program Orbit. They show the MSI and sometimes NIS fields of view plotted against a 3-d representation of the target. Often an observation continued over the course of many hours. It is impossible to capture the observation design in a single plot, but we were very pressed for time and tried to at least give the flavor of the observation in the simplest manner. Plots do not exist for every observation. Sometimes, but not always, there is a short description in the comment area on the plot itself which will help explain the observation. The times shown in the middle of the plot usually represent the bounding mets and utcs for the frames displayed. The best way to look at these sequences is with our visualization s/w, called Orbit. Even though many of these observations last hours, during which the view to Eros changes considerably, we can only show one view in these gifs. In orbit you can step through the sequence frame by frame and watch how the view to eros changes. I would like to make this program available in binary form. If you need it and want it, contact us at Cornell. We might make it available on our public ftp site.