OBJECT = COLUMN NAME = SEQ_COUNTER COLUMN_NUMBER = 1 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 1 DESCRIPTION = "CCSDS packet sequence counter." END_OBJECT = COLUMN OBJECT = COLUMN NAME = SC_TIME COLUMN_NUMBER = 2 BYTES = 4 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 3 DESCRIPTION = "Spacecraft time in integer seconds that is transmitted to the MESSENGER subsystems by the Integrated Electronics Module. This is assigned as the start time of the UVVS observation. A UVVS observation is defined as all the scan data contained within one UVVS science packet. This is due to the highly configurable nature of the instrument, i.e. it can be commanded to take multiple scans over multiple wavelengths. Unit is in mission elapsed time which is the number of seconds since launch. " END_OBJECT = COLUMN OBJECT = COLUMN NAME = PACKET_SUBSECONDS COLUMN_NUMBER = 3 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 7 DESCRIPTION = "The subsecond time in millseconds that the telemetry packet was initiated. SC_TIME plus PACKET_SUBSECONDS is the spacecraft time of the first integration. Values of this field are in units of 5 milliseconds." END_OBJECT = COLUMN OBJECT = COLUMN NAME = SPACECRAFT_POSITION_VECTOR COLUMN_NUMBER = 4 BYTES = 12 DATA_TYPE = IEEE_REAL START_BYTE = 9 ITEMS = 3 ITEM_BYTES = 4 UNIT = "KM" DESCRIPTION = "Derived (x,y,z) vector giving spacecraft position in J2000 reference frame. Reference time will be SC_TIME plus PACKET_SUBSECONDS." END_OBJECT = COLUMN OBJECT = COLUMN NAME = SUN_POSITION_VECTOR COLUMN_NUMBER = 5 BYTES = 12 DATA_TYPE = IEEE_REAL START_BYTE = 21 ITEMS = 3 ITEM_BYTES = 4 UNIT = "KM" DESCRIPTION = "Derived (x,y,z) vector giving sun position in J2000 reference frame. Reference time will be SC_TIME plus PACKET_SUBSECONDS." END_OBJECT = COLUMN OBJECT = COLUMN NAME = TARGET_LATITUDE COLUMN_NUMBER = 6 BYTES = 4 DATA_TYPE = IEEE_REAL START_BYTE = 33 UNIT = "DEGREE" DESCRIPTION = "Derived latitude on Mercury corresponding to spectral observation. Reference time will be SC_TIME plus PACKET_SUBSECONDS. Value = -999 for LIMB observations." END_OBJECT = COLUMN OBJECT = COLUMN NAME = TARGET_LONGITUDE COLUMN_NUMBER = 7 BYTES = 4 DATA_TYPE = IEEE_REAL START_BYTE = 37 UNIT = "DEGREE" DESCRIPTION = "Derived longitude on Mercury corresponding to spectral observation. Reference time will be SC_TIME plus PACKET_SUBSECONDS. Value = -999 for LIMB observations." END_OBJECT = COLUMN OBJECT = COLUMN NAME = TARGET_ALTITUDE COLUMN_NUMBER = 8 BYTES = 4 DATA_TYPE = IEEE_REAL START_BYTE = 41 UNIT = "KM" DESCRIPTION = "Derived altitude on Mercury corresponding to a spectral limb observation. Reference time will be SC_TIME plus PACKET_SUBSECONDS. =0 for non-limb observations." END_OBJECT = COLUMN OBJECT = COLUMN NAME = START_POS COLUMN_NUMBER = 9 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 45 DESCRIPTION = "Start position where grating drive begins a scan. Grating drive step position corresponds to a given wavelength being observed by an instrument." END_OBJECT = COLUMN OBJECT = COLUMN NAME = STEP_COUNT COLUMN_NUMBER = 10 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 47 DESCRIPTION = "Number of steps the grating drive will take in a scan. This directly corresponds to the range of wavelengths that will be observed in one UVVS observation." END_OBJECT = COLUMN OBJECT = COLUMN NAME = INT_TIME COLUMN_NUMBER = 11 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 49 DESCRIPTION = "Integration time in grating drive loop control interrupt periods (nominally 3000 Hz)." END_OBJECT = COLUMN OBJECT = COLUMN NAME = STEP_TIME COLUMN_NUMBER = 12 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 51 DESCRIPTION = "Step time in grating drive loop control interrupt Periods (nominally 3000 Hz)." END_OBJECT = COLUMN OBJECT = COLUMN NAME = PHASE_OFFSET COLUMN_NUMBER = 13 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 53 DESCRIPTION = "Phase offset in grating drive loop control interrupt periods." END_OBJECT = COLUMN OBJECT = COLUMN NAME = SCAN_CYCLES COLUMN_NUMBER = 14 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 55 DESCRIPTION = "Number of times to repeat scan." END_OBJECT = COLUMN OBJECT = COLUMN NAME = ZIGZAG COLUMN_NUMBER = 15 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 57 DESCRIPTION = "Indicates whether grating drive moves in a triangle motion. =0 disable, =1 enable." END_OBJECT = COLUMN OBJECT = COLUMN NAME = COMPRESSION COLUMN_NUMBER = 16 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 59 DESCRIPTION = "Selectable data size, =0 16 bit data, =1 9 bit data. Used to help determine the total number of data points contained in the observation." END_OBJECT = COLUMN OBJECT = COLUMN NAME = SLIT_MASK_POS COLUMN_NUMBER = 17 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 61 DESCRIPTION = "Indicates whether slit mask is in atmospheric (open) or Surface (closed) position. =0 Surface (closed), =1 Atmospheric (open)." END_OBJECT = COLUMN OBJECT = COLUMN NAME = FUV_ON COLUMN_NUMBER = 18 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 63 DESCRIPTION = "Indicates whether FUV PMT power is on. =0 off, =1 on." END_OBJECT = COLUMN OBJECT = COLUMN NAME = MUV_ON COLUMN_NUMBER = 19 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 65 DESCRIPTION = "Indicates whether MUV PMT power is on. A more complete description of this field can be found in the MASCS User's Guide =0 off, =1 on." END_OBJECT = COLUMN OBJECT = COLUMN NAME = VIS_ON COLUMN_NUMBER = 20 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 67 DESCRIPTION = "Indicates whether VIS PMT power is on, =0 off, =1 on." END_OBJECT = COLUMN OBJECT = COLUMN NAME = BUFFER_OVERFLOW COLUMN_NUMBER = 21 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 69 DESCRIPTION = "Indicates whether scan programmed overflowed data buffer and was therefore truncated. =0 false, =1 true." END_OBJECT = COLUMN OBJECT = COLUMN NAME = SPARE_BITS COLUMN_NUMBER = 22 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 71 DESCRIPTION = "A two-byte spare location." END_OBJECT = COLUMN OBJECT = COLUMN NAME = GD_SETTLE_CTR COLUMN_NUMBER = 23 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 73 DESCRIPTION = "Number of times during integration that the grating drive wandered outside target range." END_OBJECT = COLUMN OBJECT = COLUMN NAME = NUM_SCAN_VALUES COLUMN_NUMBER = 24 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 75 DESCRIPTION = "Total number of values or data points in the entire scan observation. Used to determine the number of valid data points in the SCAN_DATA column. Maximum value is 3626." END_OBJECT = COLUMN OBJECT = COLUMN NAME = STEP_SIZE COLUMN_NUMBER = 25 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 77 DESCRIPTION = "Step size in arcmin units." END_OBJECT = COLUMN OBJECT = COLUMN NAME = PAD_BYTE COLUMN_NUMBER = 26 BYTES = 2 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 79 DESCRIPTION = "A two-byte spare location." END_OBJECT = COLUMN OBJECT = COLUMN NAME = SCAN_DATA COLUMN_NUMBER = 27 BYTES = 7252 DATA_TYPE = MSB_UNSIGNED_INTEGER START_BYTE = 81 ITEMS = 3626 ITEM_BYTES = 2 DESCRIPTION = "Data points collected by the programmed scan observation. Data points are stored in the order in which they were collected. For example, for a two-cycle zig-zag scan consisting of grating positions A,B,C there are 6 data points which correspond to A,B,C,C,B,A grating drive step positions. Due to the fixed length nature of the table, not all items may contain valid data points. Number of valid data points is given by NUM_SCAN_VALUES. Ex. If NUM_SCAN_VALUES=1000, items 1-1000 will contain valid data points." END_OBJECT = COLUMN