VENUS EXPRESS SPICAM DATA FILES Description =========================================================================== Revisions -------------------------------------------------------- 2007 07 08 V018 update general header description and how to read the IR file 2007 01 25 V017 IR SPICAM description -reberac -nehme 2005 01 21 V016 separate UV and IR description - reberac 2005 01 05 V015 add infrared description - reberac 2004 10 12 V014 complete description dimarellis 2004 09 14 V001 initial dimarellis Purpose This document describes the contents of the IR data files which are delivered in the Spicam IR data set. Introduction =========================================================================== All informations needed to read the IR data file are given. This document is organized as: Introduction IR Data IR detectors data Content of a IR data file How to read the IR file =========================================================================== IR DATA =========================================================================== IR detectors data: =========================================================================== The SPICAM infrared channel (SPICAM-IR) is based around a scanning acousto-optical tuneable filter (AOTF). The entrance optical system comprises a lens telescope and a collimator lens, which collect the incoming radiation and direct it onto the AOTF. The two output beams from the AOTF are collimated by another lens and detected by two detectors (photodiodes with different polarization). When the AOTF is powered (at a certain frequency), it selects a wavelength which goes up to the detectors. A full spectrum for each detector is then obtained by scanning the frequencies. An infrared measurement requires several communication sessions to collect and transmit measurement data (a spectrum) from the two IR detectors. A record corresponds then to one communication session (one part of a spectrum) from the two detectors. Moreover, spectrum measurement can be done on three frequency windows, characterized by 3 parameters: FREQUENCY, POINTS and STEP. Along with spectrum measurement in three frequency windows a set of spectrum dots can be obtained during measurement cycle. Each dot represents a few adjacent spectrum points and can be viewed as a small window with predefined starting frequency, points number and frequency step. Height various sets of spectrum dots are predefined, with the possibility of 'no dots' measurement configuration. To facilitate the use of IR raw data, the SPICAM team provides data files in which spectra are reconstructed for each detector (level 0B IR data files). Spectrum points recorded by a detector for one measurement cycle are stored in the following order : spectrum points of window 0, spectrum points of window 1, spectrum points of window 2 and spectrum points of dots set defined by the command. The frequency array will contain frequencies in the following order: frequencies of window 0, frequencies of window 1, frequencies of window 2 and frequencies of dots set defined by the command Content of a IR data file =========================================================================== An IR data file contains a general header and a frequency array followed by one or several IR records. General Header : -------------- The general header contains all the general information from one SPICAM IR sequence of measurement. General Header description: =========================================================================== Integer rank Name Meaning Value Use ------------ ---- ------- ----- --- 0 Data origin = 0 or 1: on-ground = 2: in-flight 1 Data description = 0: raw data 2 File creation date year 3 month 4 day 5 hour 6 min 7 sec 8 ITYPE Data identification = 48: SPICAM simulated data ground = 49: SPICAM flight data = 40: SPICAM flight data 9 Mission = 1: Mars express = 2: Venus express 10 BE mode = 0: dummy TC = 1: TestN = 2: TestS = 3: not used = 4: Limb = 5: StarLimb1 = 6: StarLimb2 = 7: StarLimb3 = 8: Nadir1 = 9: Nadir2 = 10: Nadir3 = 11: Align = 12: TiProg = 13: Sun1 = 14: Sun2 = 15: Sun3 11 Sampling period 12 Peltier activation = 0: off = 1: on 13 Pre-cooling duration (Peltier) 14 Nadir Shutter status = 0: closed = 1: open = 2: opening = 3: closing 15 Solar Shutter status = 0: closed = 1: open 16 SOIR channel = 0: off activation = 1: on 17 Software used to = 0: spi_dds2ir0B (VEX) produce this file 18 Exit = 0: lab mode = 1: flight mode 19 Source = 0: host command = 1: ROM command 20 dets = 0: detector 0 = 1: detector 1 = 2: detector 0&1 = 3: AOTF 21 swap dets = 0: detectors 0&1 to ADC 0&1 = 1: detectors 0&1 to ADC 1&0 22 time = 0: 1.4 ms = 1: 2.8 ms = 2: 5.6 ms = 3: 11.2 ms = 4: 22.4 ms = 5: 44.8 ms = 6: 89.6 ms = 7: 179.2 ms 23 dac 24 gain boost = 0: 1 = 1: 4 25 gain = 0: 1 = 1: 2 = 2: 4 = 3: 8 = 4: 16 = 5: 32 = 6: 64 = 7: 128 26 Reference = 4375 Frequency(kHz/16) 27 Window 0 frequency = 0 by default for SPICAM offset (in frequency step) 28 Window 0 frequency = 1 : LW range (70 to 140 MHz) range = 2 : SW range (140 to 280 MHz) 29 Window 0 points = 0 to 4095 30 Window 0 step = 0 to 15 31 Window 1 frequency = 0 by default for SPICAM offset (in frequency step) 32 Window 1 frequency = 1 : LW range (70 to 140 MHz) range = 2 : SW range (140 to 280 MHz) 33 Window 1 points = 0 to 4095 34 Window 1 step = 0 to 15 35 Window 2 frequency = 0 by default for SPICAM offset (in frequency step) 36 Window 2 frequency = 1 : LW range (70 to 140 MHz) range = 2 : SW range (140 to 280 MHz) 37 Window 2 points = 0 to 4095 38 Window 2 step = 0 to 15 39 Command descriptor 40 Dots descriptor 41 Timing error + UART time-out+ command format error+ NACK counter + Time-out 42 Expected points/spectrum 43 Number of spectra 44 Number of sessions/spectrum 45 to 49 Free Single Record Header description: =========================================================================== Integer rank Name Meaning Value ------------ ---- ------- ----- 0 UTC time of the year (integer) 1 first session of month (integer) 2 the measurement day (integer) 3 cycle hour (integer) 4 (board time) minute (integer) 5 second (integer) 6 msecond (float) 7 Temperature of (level 0-255) (integer) SU TRP1 8 Temperature of (level 0-255) (integer) SU TRP2 9 Temperature of solar Shutter (level 0-255) (integer) 10 Temperature of Structure (level 0-255) (integer) 11 Temperature of detector 0 in volts (float) 12 Temperature of detector 1 in volts (float) 13 Temperature of AOTF in volts (*166) (float) 14 Temperature of baseplate in volts (*166) (float) 15 RF power at 110 MHz in volts (float) 16 Reference voltage in volts (float) 17 Main SPICAM LCL current (level 0-255) (integer) How to read the IR file: =========================================================================== To read IR data file DO: Open the file Read General Header (50 parameters (50*2 bytes)) Read Frequency Array (ExpectedPoints float (ExpectedPoints*4 bytes)) Loop Until EOF Read Time (6 integer+1 float) and satellite and monitor's values (see type above) Read Spectrum 1 (ExpectedPoints float) Read Spectrum 2 (ExpectedPoints float) (IF Channels equal 2) Goto Loop