Description of NIS Mirror Geometry Test Feb 1, 2000 (32/0640) The objective of this test was to determine the actual angular spacing of the NIS mirror positions. The NIS mirror rotates about an axis parallel to the spacecraft y axis. Therefore, viewing through these mirror positions is in the spacecraft x-z plane. Strategy was to perform a spacecraft slew that would position Eros at a starting position somewhere in the NIS mirror viewing plane. We then position the NIS mirror to position 'n', so that Eros is just outside the fov. A slow controlled slewing scan begins which moves Eros through the fov; Eros is moving in the x-z plane and passes through the narrow width of the fov. After Eros has passed through the fov, we quickly advance the mirror two positions (to n+2). Eros then passes through position (n+2). The slewing scan continues, while leapfrogging the NIS mirror positions until the end of the mirror positions available in that direction. The process is then reversed, going the other direction, but this time we do the NIS positions not done before. For instance, if we do even the first time, we do odd on the return. Due to spacecraft solar panel pointing constraints it was not possible to cover all of the NIS mirror positions. We could only test NIS 45 through 200. Unfortunately we could not test in the region of NIS 300 which is in the vicinity of where low phase flyover would be performed. approx s/c +x NIS 75 NIS 30 ^ _ | /| |30 / |deg/ | / | / NIS 300 <----------------|/ approx s/c -z (scans, secbetwscans, obs/scan, calint, spec/obs, rests, darks, mirrorstep/obs, secbetweenobs) Seq 15 (1,0,1,1,1,0,0,0,0) Seq 14 (58,0,1,1,1,0,0,0,0) performs 58 'scans' (1 scan = 1 obs that is 1 second long) NIS Mirror Geom 1 (32/0640): - Acquire data through NIS 78 through 46 (EVENs), and NIS 47 through 77 (ODDs) -600 Slew to put Eros center at the center of NIS mirror pointing position 78 (where NIS 78 would point). Set up NIS to actually put mirror at position 76. 0 Begin scan that moves Eros at .01333 deg/sec exactly in the x-z plane (takes 30 sec to move from 1 NIS mirror position to another) toward decreasing mirror positions. Execute Seq 15 (a single 1 sec spectrum) 30 Eros is now at NIS77. Begin NIS Superscan_2 (14,76,SLIT,10X,16,BACKWARD). This executes Seq 14 at 16 different mirror positions, starting with NIS76, stepping 2 mirror positions backward for each new execution. Sequence 14 takes 58 individual 1 second spectra. There is a 2 second pause between each execution of Seq 14 to move the mirror. Therefore Seq 14 executes begin at 60 second intervals (the same amount of time it takes Eros to move through the angular distance of 2 mirror positions). At the start of the first execution of Seq 14 (through NIS 76), Eros is actually sitting at NIS 77, completely outside the view of NIS 76. Through the course of the execution of Seq 14, Eros moves into, passes through, and then completely out of NIS 76 while the 58 individual spectra are taken through NIS 76. In the diagram below, the spacecraft is the fixed reference frame. I am depicting the slew by showing Eros move through the various NIS mirror positions. A NIS fov box is shown for those mirror positions that data is acquired through during this first NIS Superscan. Executions of Seq 14: 1 2 3 15 16 Execution1 begins when Eros is here | Mirror Pos: 78 | 76 74 72 48 46 | ___ ___ ___ ___ ___ V | | | | | | | | | | . . | . | . | . | . | . | . etc. . | . | . | . | start | | | | | | | | | | eros |___| |___| |___| |___| |___| | | | | time 0 60 120 180 -----------------------> direction of eros movement relative to s/c reference frame |----->| eros covers 2 fov widths in 60 sec during 1st execution of seq 14 at NIS76 960 The scan ends when Eros is at NIS position 46. We reach that position half way through the final (16th) execution of Sequence 14 (30 seconds into it). Then we wait at that position for 60 seconds before scan reverses direction. During this time the second half Seq 14 completes (the 2nd 30 seconds of integration occurs when Eros is stopped at position 46). And then there is 30 seconds of pad before the scan (the slew) reverses direction. 1020 Reverse slew direction to start moving Eros to higher mirror positions. Begin Superscan_2 (14,47,SLIT,10X,16,FORWARD). NIS mirror is moved to position 47 as initial setup. Seq 14 is executed at 16 positions starting with NIS 47, advancing 2 positions for each execution. Same as above, one exectuion every 60 seconds. Executions of Seq 14: 16 15 14 2 1 Begin 1st execution of Seq 14, at 1020 Mirror Pos: 77 75 73 49 47 | ___ ___ ___ ___ ___ | | | | | | | | | | | V slew ends, eros at--> . | . | . | . | . | . | . etc. . | . | . | . | . <-- slew starts, eros here at 1020 position 78 | | | | | | | | | | |___| |___| |___| |___| |___| | | | | | | 1980 1920 1860 1080 1020 time <------------| direction of eros movement relative to s/c reference frame |<------| eros covers 2 fov widths in 60 sec during 1st execution of seq 14 at NIS47 MSI Mirror Geom 1 - ----------------- Note- Eros was only viewable by the MSI fov when Eros was in the range of NIS 72 - 79 approximately. Below times use timescale given in NIS description (above). At time = 30, begin taking one filter 4, table5/fast image every 12 seconds for a total of 17 images. This covers the time during the start of the first slew when Eros is in the MSI fov. At time = 1818, take one filter 4, table 5/fast image every 12 seconds for a total of 20 images. This should cover the time when Eros is back in MSI fov at the end of NIS Mirror Geom 2. NIS Mirror Geom 2 (36/0110): --------------------------- - Acquire data through NIS 75 through 199 (ODDs), and NIS 200 through ??? (EVENs) (Time = 0 at 36/0110) -600 Slew to put Eros center at the center of NIS mirror pointing position 73. Set up NIS to actually put mirror at position 75. 0 Begin scan that moves Eros at .01333 deg/sec exactly in the x-z plane (takes 30 sec to move from 1 NIS mirror position to another) toward increasing mirror positions. Execute Seq 15 (a single 1 sec spectrum) 30 Eros is now at NIS74. Begin NIS Superscan_2 (14,76,SLIT,10X,63,FORWARD). This executes Seq 14 at 63 different mirror positions, starting with NIS75, stepping 2 mirror positions forward for each new execution. Sequence 14 takes 58 individual 1 second spectra. There is a 2 second pause between each execution of Seq 14 to move the mirror. Therefore Seq 14 executes begin at 60 second intervals (the same amount of time it takes Eros to move through the angular distance of 2 mirror positions). At the start of the first execution of Seq 14 (through NIS 75), Eros is actually sitting at NIS 74, completely outside the view of NIS 75. Through the course of the execution of Seq 14, Eros moves into, passes through, and then completely out of NIS 75 while the 58 individual spectra are taken through NIS 75. In the diagram below, the spacecraft is the fixed reference frame. I am depicting the slew by showing Eros move through the various NIS mirror positions. A NIS fov box is shown for those mirror positions that data is acquired through during this first NIS Superscan. Executions of Seq 14: 63 62 61 2 1 Begin 1st execution of Seq 14 Mirror Pos: 199 198 197 77 75 | ___ ___ ___ ___ ___ | | | | | | | | | | | V . | . | . | . | . | . | . etc. . | . | . | . | . . | | | | | | | | | | eros starts at 73 ^ |___| |___| |___| |___| |___| | scan ends when | | | | eros is at pos 200 60 0 time <---------------| direction of eros movement relative to s/c reference frame |<------| eros covers 2 fov widths in 60 sec during 1st execution of seq 14 at NIS75 3780 The scan ends when Eros is at NIS position 200. We reach that position at the end of the integration time for 63rd execution of Sequence 14. Then we wait at that position for 60 seconds before direction of slew is reversed. 3810 In the meantime, half way through that 60 second wait time, we begin Superscan_2 (14,200,SLIT,10X,64,BACKWARD) (NIS mirror has bee set to be at position 200). Seq 14 is executed at 64 positions starting with NIS 200, decreasing 2 positions for each execution. Same as above, one exectuion every 60 seconds. EXCEPT, the first 30 seconds of the 1st execution (through NIS 200) is done when eros is sitting still at position 200. 3840 Slew direction reverses, eros begins to move to lower mirror positions at a rate of 2 positions every 60 sec. The 2nd 30 seconds of 1st execution of Seq 14 is done while Eros moves from position 200 to position 199. Normal operations resume from there on where on execution of Seq 14 occurs as Eros passes in and out of every other fov. Executions of Seq 14: 1 2 3 63 64 |-Execution1 begins when Eros is here at time 3810, eros only moves from 200 to 199 during this execution | |-Execution 2 begins when Eros is here at time 3870, everything normal from now on, eros moves 2 fov per seq 14 execution V | |-Execution 3 begins when eros is here at 3930 | | |-Execution 64 begins here at 7620 Mirror Pos: 200 | 198 | 196 76 | 74 ___ V ___ V ___ ___ V ___ | | | | | | | | | | | . | . | . | . | . | . etc. . | . | . | . | . start | | | | | | | | | | eros |___| |___| |___| |___| |___| | | | | | time 3840 3900 3960 7560 7650 Slew ends with Eros at pos 73 |----------------------> eros doesn't begin to move until 3840, moves to lower mirror positions |----->| eros covers 2 fov widths in 60 sec during 2nd execution of seq 14 at NIS198 MSI Mirror Geom 2 - ----------------- Note- Eros was only viewable by the MSI fov when Eros was in the range of NIS 72 - 79 approximately. Below times use timescale given in NIS description (above). At time = 30, begin taking one filter 4, table5/fast image every 12 seconds for a total of 15 images. This covers the time during the start of the first slew when Eros is in the MSI fov. At time = 7410, take one filter 4, table 5/fast image every 12 seconds for a total of 20 images. This should cover the time when Eros is back in MSI fov at the end of NIS Mirror Geom 2.