Detailed Description - XREQs See /eros/descript/xreqs.xls for spreadsheet that contains only XREQ observations. During the low orbits (50km A, B, C, and 35km A, B, C), the MSI team did not have control of pointing for the bulk of the observing time. Each day during these orbits we had usually an 8 hour downlink pass with an opnav before and after each pass, and one in the middle of the observing period. These were generally 35 minute periods decicated to each opnav. The remainder (amounted to about 14 hours daily) was given over to the Eros low mapping observation effort controlled predominantly by the XGRS team. For the first two weeks (00122 and 00129), pointing for the mapping periods was controlled by NLR and these were almost all nadir pointed (a few in 00129 were 1.5 deg off nadir). The XGRS team took over pointing control for the remainder. They generally they would point between 3 and 5 deg off nadir (sunward) and hold for long periods. Occaisionally they pointed to some abf position for an hour or so. As they were mostly interested in moderately low emission, they did not point much to the polar region. Hence there is not a lot of 50km data of the north pole. We scheduled MSI to ride along with this pointing. We basically took available downlink and spaced the images evenly throughout the Eros observing periods, making sure that frame-to-frame overlap never dropped below 10-15 percent. There is one observation (i.e., MSI_XREQ09_352a) for each period between opnavs. The pointing is archived in the XGRS area. Orbital periods for 50 and 35km orbits are about 1.2 and .8 days, respectively. In the polar orbits (50km A and B) the spacecraft passes over each pole every half day. Since Eros is spinning below once every 5.3 hours, when the spacecraft is over a pole the image strips appear appear to spin at the poles. As the latitude falls, the strip gradually spirals around the asteroid toward the other pole. We did not try to predict when the asteroid surface would be lit or dark because of the uncertainties in navigation when we delivered these sequences. We just took frames throughout each entire observing period, and thus many frames are dark. Monochrome: ---------- The great bulk of the data is monochrome, filter 4 but we cycled through different imaging schemes, changing compression or whether or not they were clean. This is easiest to see in the spreadsheet (SEQ ID column). - For the first 3 weeks (00122, 00129, 00136), we used: seq 1 - One Filter 4 image, FAST/Table 6, autoexposure - But starting with week 00143 we alternated the imaging seq def for each new xreq observation: seq 30 - Two Filter 4 images, FAST/Table 5, manual exposures 103 and 0. (this is 'clean') seq 18 - One Filter 4 image, FAST/Table 5, autoexposure seq 9 - Two Filter 4 images, FAST/no lossy compression, manual exposures 103 and 0 (this is 'clean') seq 8 - One Filter 4 image, FAST/ no lossy compression, autoexposure There were usually two 'XREQ' observations per day, scheduled between the three opnav periods. Color: ----- During the 35 km B, a number of color flyovers were acquired with the xgrs mapping pointing. These are described in the color35.txt file. See also Chapter 22, Color Flyovers 35km B. XREQ PLOTS AND MAPS: For each week during this period there is a total coverage plate map. This is a cylindrical projection showing minimum emission angle captured on each plate imaged during the week with these observations. Best way to understand the coverage during different parts of the year is to look through these plots. These are located in the week subdirectory: 50 km A /eros/00122/xreq_00122.gif /eros/00129/xreq_00129.gif /eros/00136/xreq_00136.gif /eros/00143/xreq_00143.gif /eros/00150/xreq_00150.gif /eros/00157/xreq_00157.gif /eros/00164/xreq_00164.gif /eros/00171/xreq_00171.gif /eros/00178/xreq_00178.gif /eros/00185/xreq_00185.gif 35km A /eros/00192/xreq_00192.gif /eros/00201/xreq_00201.gif /eros/00205/xreq_00205.gif 50km B /eros/00212/xreq_00212.gif /eros/00220/xreq_00220.gif /eros/00227/xreq_00227.gif /eros/00234/xreq_00234.gif 50km C /eros/00290/xreq_00290.gif 35km B /eros/00346/xreq_00346.gif /eros/00353/xreq_00353.gif /eros/00360/xreq_00360.gif /eros/01001/xreq_01001.gif /eros/01008/xreq_01008.gif /eros/01015/xreq_01015.gif 35km C /eros/01030/xreq_01030.gif These plots were made by projecting all of the frames from all XREQ observations during the week onto the shape model. A program written by Brian Carcich then finds each plate within each frame and determines emission and other viewing angles. Although many plates were imaged by multiple different frames, we have sorted through and found the minimum emission angle achieved during that week for each plate. What is not shown is the incidence when that emission angle was captures (generally poor). But at least this gives a feel for the coverage, and where low emission is available. There are orbit plots (linked from Predict column in spreadsheet) for selected groups or individual observations to give the feel for how the strips looked during the different phases. These are only moderately useful because you can only see one side of the planet, and the shadowing is only good for one of the images (the red-lined frame).