PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT PUBLICATION_DATE = 2001-07-20 NOTE = "Description of the EROS_OBSV_GUIDE files in this directory." END_OBJECT = TEXT END Column Descriptions for the MSI Eros Observation Guides: The MSI Eros Observation Guides are spreadsheets that describe some basic information about each MSI observation that was acquired during the NEAR mission starting with 1998-210. There is one line per observation. An 'observation' is a convenient unit for organizing the data and refers to the process of sequencing. The observations within the Eros guides were developed using the SEQGEN software. This is in contrast to the sequences prior to 1998 which were built by hand using STOL. A different organizational structure for the supporting files was required for each which is why the spreadsheets were divided in this manner. The following fields are recorded: 1. Orbit An entry in this column identifies when an orbit correction maneuver was performed. By example, when a value reads "325x266" it means that on that day, the spacecraft entered into an elliptical orbit with radii of 325x266 km. More information about spacecraft orbital position and viewing geometry can be found in the eros_orbital_info.txt file. See also the observation_overview.txt file; in chapter 13 there is a table of maneuvers performed during the orbital mission. 2. Sub-solar Latitude - latitude of a point on Eros where a line connecting the sun and Eros center pierces the surface 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. In the sequence files, (i.e., 00066_final_sasf.txt) a single 'Request' usually corresponds to one observation in this spreadsheet. The names will be similar but not always identical. Occasionally a Request is broken into several observations. 4. Year-Doy This describes the year and day of year of the start of the observation. 5. Sequence - In the Eros spreadsheets, this column refers to a subdirectory which corresponds to the 'sequencing week' during which that observation was created. Sequences were generated once per week (duration 1 week) during the orbital phase and were identified by this 5 digit integer which essentially tells you the year and doy of the start of that sequence (98306 was the sequence that started on or about doy 306, 1998). In the corresponding subdirectory you will find the gif plots for that weeks observations, the sequence file (98306_final_sasf.txt), the imagelist (98306.imagelist), and the expanded command files (98306.msi and 98306.nis). More information about interpreting these files can be found in eros_seq_archive.txt. 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 This column lists all SEQ IDs called for execution during the observation. Up to 30 unique Sequence Definitions were resident in the MSI DPU during the Eros mission phases. Each of these 30 Sequence Definitions contains a parameter, the Seq ID, which is an integer between 1 and 30, 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). They 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. For the most part, we were able to keep the set of 30 constant for most of the orbital phase but various factors required that some of them be changed periodically. The msi_seqid_log.txt contains a log entry for each Seq ID, sorted by time, every time that Sequence Definition was changed. It also describes the fields within a Sequence Definition. Often more than one Seq Def was used within a given observation. For instance, Seq IDs 20 and 19 were often used to take the 3 color 'cleaned' observations. The auto exposures were taken with Sequence 20, and manual zero exposures were taken with Sequence 19 and they were executed within an observation as a pair. An alternative way to know what compression, exposures, filters, etc were used in an observation is to look in the individual image headers. The imagelist is also a good source to get an overview, but it does not give compression info (i.e., eros/00066/00066.imagelist) 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 is a shortcut description of the type of compression used for the images acquired in this observation. Generally, during the 2000 data, when it says Table5, it means Table5, ON, FAST. When it ways Lossless, it means NONE, ON, FAST. See SeqIDs for more detail. Compression info is also available in the image header. 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 main /eros subdirectory. The observation_overview.txt also contains detailed descriptions of many observations. 15. Gifs - These are predict plots generated by our visualization program Orbit. They show the MSI and sometimes NIS fields of view plotted onto a 3-d representation of Eros shape. 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 colored axes represent the asteroid body fixed system in Eros. The red axis is the +X, prime meridian (0 longitude). The green axis is +Y, which is 90 E long, or 270 W long. The blue axis is the north pole of Eros, it is also the spin pole, +Z, for the right-handed system these axes make up. Direction of spin of Eros is determined by putting right thumb in direction of blue axis, fingers pointing along +X, red axis, then curl fingers. The direction in which your fingers curl is the direction that Eros is spinning. The times shown in the middle of the plot usually represent the bounding mets and utcs for the frames displayed.