NIMS Ikernel wds 890613 900627 Last element of time table corrected, focal length added, typos fixed. (RMX) 900423 modify long map wait cycle (two ending 3's) 900221 Modification for VENUS & Earth 1 901009 Change mirror time_table to reflect two rest points Set boresight offset equal 0 until direction known ***************************************************************** *Assumptions to be used until measurements on stars are analyzed* * 1. NIMS boresight lies between MP 9 and 10 (mp 0-19) * * 2. NIMS boresight is displaced from the L vector (SSI * * boresight by approximately 0.25 milliradians in both * * cone and cross-cone. There is an uncertainty in the * * sign of this displacement, so software should, at * * present, allow for an adjustable offset. Until the * * sign and magnitude of the boresight offset is known, * * a value of 0 should be used. * * 3. The timing of acquistion of data for a given mirror * * position shall be - The 0th mirror position occurs * * on RTI 0 of a minor frame. Each minor frame has 40 * * mirror positions sampled at even time intervals. * * This assumption is not exactly correct, so software * * should allow for a timing lookup table in the I * * kernel. * * 4. The mirror is assumed to move in increments of pure * * cross cone. Software should allow for lookup of a * * cone displacement - now assumed to be 0. * * 5. Each mirror displacement is assumed to be exactly 1 * * FOV, 0.5 milliradians. This is reflected in the * * x-cone displacement table * * 6. The mirror displacements are assumed to be * * independent of temperature. * * 7. The first mirror motion direction is assumed to be * * down. * ***************************************************************** In one minor frame (2/3 second) the mirror moves down 20 mirror positions and up 20 mirror positions. Due to mirror hysteresis, the up positions are not the same as the down positions. Starting direction (first 1/3 second) is TBD. (see assumptions) Mirror has two speeds - moving and stopped (no flyback speed for defined NIMS modes) and two rest positions: mirror position 0 for wait and mirror position 9.5 for off. For a given mode, the mirror has a particular cycle. LONGMAP 12 MF cycles, 1 MF wait = 8 2/3 seconds = 7 repeats/RIM FULLMAP 6 MF cycles, 1/2 MF wait = 4 1/3 seconds = 14 repeats/RIM SHORTMAP 3 MF cycles, 1/2 MF wait = 2 1/3 seconds = 26 repeats/RIM FIXEDMAP 6 MF cycle , 1/2 MF wait = 4 1/3 seconds = 14 repeats/RIM BANDEDGEMAP 1/2 MF cycle, 1/2 MF wait = 2/3 seconds = 91 repeats/RIM (note - the "cycle" for bandedge actually is 4/3 seconds (two wavelengths) - it is defined as above to accomodate the scan mirror cycle.) SPECTROMETER - mirror is fixed on boresight - different position than wait position, mirror cycles have no meaning) (cycle here refers to a complete mirror scan - up and down) The timing of each mirror position is NOMINALLY 1/40 of 2/3 second. The actual timing depends on the internal operation of the instrument. The NIMS I kernel will provide a) an offset of the NIMS boresight from the spacecraft L vector, b) mirror position tables in cone and cross-cone for the various NIMS mirror states c) a mirror timing table representing the sample time for each mirror position, d) Mode_RIM tables, which point to the correct mirror position table for each 1/2 minor frame in a rim (for each NIMS mode) and e) the focal length of the telescope. Additional tables may be needed if new modes are added to NIMS and/or if the mirror positions or focal length evolve with time or temperature. a. The NIMS boresight offset from the s/c boresight has two values in milliradians: cone and cross cone. b. The mirror position tables have 20 values each and cover the time interval of 1/2 minor frame. The tables state the offset from the NIMS nominal boresight in crosscone in milliradians. Nominal increment is 0.5 MR. Similarly, the cone offset tables state the offset in cone. Nominal offset is 0.0. The NIMS nominal boresight is at mirror position 9.5 counting the first position as 0. This is the mirror off position. The NIMS wait position is at mirror position 0. The mirror normally arrives at this position with a normal scan (except for reset conditions at the RIM rollover). The NIMS offset tables consist of the following (for both cone and cross_cone). Table 1 - SCAN DOWN Table 2 - SCAN UP Table 3 - WAIT Table 4 - OFF These tables cover 1/3 second (1 NIT = 1/2 minor frame). Note that it is necessary to combine two tables to describe mirror motion for a minor frame. This is done by pointers in the mode rim table c. The mirror timing table has 40 values corresponding to the sample time for each mirror position in a minor frame. Time is in milliseconds from start of minor frame. Additional tables may have to be added if it is found that the NIMS sample times vary for different modes. d. Mode rim tables contain 182 entries corresponding to the mirror state for a given mode in a given 1/2 minor frame within a rim. These tables merely point to the correct mirror position table for a given mode. These rim tables are: LONG MAP FULL MAP SHORT MAP FIXED BANDEDGE SPECTROMETER (valid for all grating cycle modes). Combination modes, such as stop and slide, are not described here, since they are decomposed into their primitive modes prior to geometry generation. Example: (nominal values) (assume boresight = position 9.5) all positions in milliradians a. offsets boresight_xcone_offset = 0. boresight_cone_offset = 0. b. Mirror position tables 1. Position_table_xcone_down -4.75, -4.25, -3.75, -3.25, -2.75, -2.25, -1.75, -1.25, -0.75, -0.25, 0.25, 0.75, 1.25, 1.75, 2.25, 2.75, 3.25, 3.75, 4.25, 4.75, 1a. Position_table_cone_down 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00 2. Position_table_xcone_up 4.75, 4.25, 3.75, 3.25, 2.75, 2.25, 1.75, 1.25, 0.75, 0.25, -0.25, -0.75, -1.25, -1.75, -2.25, -2.75, -3.25, -3.75, -4.25, -4.75 2a. Position_table_cone_up 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00 3. Position_table_xcone_wait -4.75, -4.75, -4.75, -4.75, -4.75, -4.75, -4.75, -4.75, -4.75, -4.75, -4.75, -4.75, -4.75, -4.75, -4.75, -4.75, -4.75, -4.75, -4.75, -4.75 3a. Position_table_cone_wait 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00 4. Position_table_xcone_stop 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00 4a Position_table_cone_stop 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00 c. Mirror sample timing table Assumes the end points are at the beginning of two minor frames. There are two pauses, one after mirror position 19 and one after mirror position 39. The ratios given are the ractional distance in time between the two end points. The first end point (0.0) is at the start of the first minor frame and the second end point (1.0) is at the start of the next minor frame. An example interpolation is shown for interpolating right ascension for a given mirror position: RAINT=RA(1)+(RA(2)-RA(1))*RATIO(MP+1) Time_table 0.00000000, 0.02380952, 0.04761905, 0.07142857, 0.09523810, 0.11904762, 0.14285715, 0.16666667, 0.19047619, 0.21428572, 0.23809524, 0.26190478, 0.28571430, 0.30952382, 0.33333334, 0.35714287, 0.38095239, 0.40476191, 0.42857143, 0.45238096, 0.50000000, 0.52380955, 0.54761904, 0.57142860, 0.59523809, 0.61904764, 0.64285713, 0.66666669, 0.69047618, 0.71428573, 0.73809522, 0.76190478, 0.78571427, 0.80952382, 0.83333331, 0.85714287, 0.88095236, 0.90476191, 0.92857140, 0.95238096 d. MODE_RIM tables Longmap= 1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,3,3, 1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,3,3, 1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,3,3, 1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,3,3, 1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,3,3, 1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,3,3, 1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,3,3 Fullmap= 1,2,1,2,1,2,1,2,1,2,1,2,3,1,2,1,2,1,2,1,2,1,2,1,2,3, 1,2,1,2,1,2,1,2,1,2,1,2,3,1,2,1,2,1,2,1,2,1,2,1,2,3, 1,2,1,2,1,2,1,2,1,2,1,2,3,1,2,1,2,1,2,1,2,1,2,1,2,3, 1,2,1,2,1,2,1,2,1,2,1,2,3,1,2,1,2,1,2,1,2,1,2,1,2,3, 1,2,1,2,1,2,1,2,1,2,1,2,3,1,2,1,2,1,2,1,2,1,2,1,2,3, 1,2,1,2,1,2,1,2,1,2,1,2,3,1,2,1,2,1,2,1,2,1,2,1,2,3, 1,2,1,2,1,2,1,2,1,2,1,2,3,1,2,1,2,1,2,1,2,1,2,1,2,3 Shortmap= 1,2,1,2,1,2,3,1,2,1,2,1,2,3,1,2,1,2,1,2,3,1,2,1,2,1, 2,3,1,2,1,2,1,2,3,1,2,1,2,1,2,3,1,2,1,2,1,2,3,1,2,1, 2,1,2,3,1,2,1,2,1,2,3,1,2,1,2,1,2,3,1,2,1,2,1,2,3,1, 2,1,2,1,2,3,1,2,1,2,1,2,3,1,2,1,2,1,2,3,1,2,1,2,1,2, 3,1,2,1,2,1,2,3,1,2,1,2,1,2,3,1,2,1,2,1,2,3,1,2,1,2, 1,2,3,1,2,1,2,1,2,3,1,2,1,2,1,2,3,1,2,1,2,1,2,3,1,2, 1,2,1,2,3,1,2,1,2,1,2,3,1,2,1,2,1,2,3,1,2,1,2,1,2,3 Fixedmap= 1,2,1,2,1,2,1,2,1,2,1,2,3,1,2,1,2,1,2,1,2,1,2,1,2,3, 1,2,1,2,1,2,1,2,1,2,1,2,3,1,2,1,2,1,2,1,2,1,2,1,2,3, 1,2,1,2,1,2,1,2,1,2,1,2,3,1,2,1,2,1,2,1,2,1,2,1,2,3, 1,2,1,2,1,2,1,2,1,2,1,2,3,1,2,1,2,1,2,1,2,1,2,1,2,3, 1,2,1,2,1,2,1,2,1,2,1,2,3,1,2,1,2,1,2,1,2,1,2,1,2,3, 1,2,1,2,1,2,1,2,1,2,1,2,3,1,2,1,2,1,2,1,2,1,2,1,2,3, 1,2,1,2,1,2,1,2,1,2,1,2,3,1,2,1,2,1,2,1,2,1,2,1,2,3 Bandedge= 1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2, 1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2, 1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2, 1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2, 1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2, 1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2, 1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2 Spectrometer= 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4, 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4, 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4, 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4, 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4, 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4, 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4 e. The focal length of the NIMS telescope is nominally 8 mm. Instantaneous boresight is at cone coneangle + offset + mirror offset (at mirror position) crosscone crossconeangle + nims offset + mirror offset (at mirror_position) where time = RIM + mf + time_table(mirror position +1)*666.667MSEC where mirror offset = position_table(mirror_position,MODE_RIM(nit,mode)) Questions yet to be answered.... Is there a mirror turn-around time? Is wait at top or bottom of mirror cycle? Is the mirror position the same at MP 20 and 21? (counting from 0) What is the boresight mirror position. Does it match any mirror position? Is the initial mirror motion up or down (relative to mounting feet, image inversion etc.) What is the detailed mirror timing (with respect to acquisition).