urn:esa:psa:context:instrument:mex.spicam 1.0 1.11.0.0 Product_Context urn:nasa:pds:context:instrument:spicam.mex 2021-02-24 1.0 Changed inst LIDs from u:n:p:c:i:instID.scID to u:n:p:c:i:scID.instID Changed LIDs from urn:nasa:pds: to urn:esa:psa: And per "Guide toPDS4 Context Products" v1.7, changed all lidvid_reference to lid_reference urn:esa:psa:context:instrument_host:spacecraft.mex instrument_to_instrument_host Mars Express SPICAM Light Flight User Operations Manual, ref SP-DES-032, issue 004,Apr 17 2002, Dimarellis, E., Service d'Aeronomie du CNRS. reference.SPFUM408 SPICAM Spectrometer not applicable not applicable MARS EXPRESS SPICAM Description =============================== Revisions ---------- 2004 09 14 V001 initial Dimarellis Purpose This document describes the SPICAM (SPectroscopy for the Investigation of Characteristics of the Atmosphere of Mars) instrument on Mars express mission. Introduction ============= In this document all technical details concerning the Spicam instrument are given. The mechanical and electrical characteristics are listed. The optical interfaces with spacecraft and the fields of view are explicit. This document is organized as: Introduction Instrument summary Design Description Physical configuration Subsystems Instrument summary: =================== SPICAM Light is a collaboration of -Service d'Aeronomie, Verrieres le Buisson, France; -IASB, Bruxelles, Belgique and -IKI, Moscow, Russia. The Spicam Light instrument is made of 2 boxes. The first box called DPU acts as the main electronic interface with the Spacecraft. The other is the sensor box or unit. This sensor unit has one channel in the ultraviolet wavelength range - 118-320 nm - (named SUV), and another one (named SIR) in the near infrared wavelength range - 1.1-1.7 micrometers. SPICAM Light Main characteristics summary Table: Spectral bands 118 - 320 nm (UV) 1.1 - 1.7 microns (IR) Spectral sampling UV: 0.55 nm/pix IR: 0.8 nm/pix at 1.5 micron Mass DPU 0.71 kg SU 4.14 kg Total 4.85 kg Power DPU+SU 17 W to 26 W Volume DPU: 1.65 x 1.14 x 0.65 dm3 SU: 4 x 2.4 x 1.15 dm3 Data rate 9 and 34 kbit/s (averaged over several seconds) Data Volume 100 - 300 Mbits / day Observations One Board Time TC, One Spicam TC Duration: 5 to 30 mn Pointing (orientation) Inertial Star Inertial Sun Nadir Design Description: =================== The Sensor Unit is made of: the servitudes channel the UV channel the IR channel The Sensor Unit has two openings for Nadir viewing, one for UV channel, the other for IR channel located on the Nadir face of S/C. In addition, there is an opening for Solar viewing. This Solar aperture is NOT on the S/C Nadir face. The Sensor Unit has two mechanisms, one which move On and Off a slit in the UV channel, the other which moves a shutter on the Solar aperture. Spicam mechanisms are fully autonomous and no separate commands are needed for mechanism operations. Each mechanism has two statuses, ON and OFF for slit, OPEN and CLOSED for shutter. The UV channel is a spectrometer with an optical baffle, an off axis parabolic mirror, a slit with two positions, a grating and a detector which an intensified CCD. On the CCD, the rows which are parallel to the unit baseplate, are the spectral dimension. The IR channel is made of an entrance lens, an AOTF and two single pixels detectors (for each polarisation). As the AOTF acts as a filter, the IR spectrum is obtained by electrically scanning the AOTF frequency. All the channels have their own digital electronics which performs all operations at detector level and digitizes the data, then waiting for transmission to the DPU through a RS422 link at 937 kbits/s. The DPU main functions are: electrical interfaces with S/C send commands and get data from the subunits formatting data before transmission to S/C The DPU has the general control of the instrument. It sends commands to the sub units and retrieves data. Then it formats and produces telemetry packets. Servitudes refers to non-detector elements of Sensor Unit. The polling of the sub units is done by the DPU, at a rate defined in the Telecommand. Depending on the operating mode, The IR channel is switched ON or not. Physical configuration: ======================= The Sensor Unit has two main directions of sight, one is Nadir ( s/c +Z), the other is 'behind' Solar panel, -Y side. The Sensor Unit has two openings for Nadir viewing, one for UV channel, the other for IR channel located on the Nadir face of S/C. The instrument optical axis is parallel to the baseplate and perpendicular to the Nadir face of the spacecraft. The Sensor Unit has three apertures: - Main UV aperture on Nadir face. - IR aperture on Nadir face. - Secondary UV and IR aperture for Sun viewing internal mirrors and fibre bent the Solar light in the instrument main optical axis In addition, there is an opening for Solar viewing. This Solar aperture is not on the S/C Nadir face. The Solar viewing opening opening is built in the base plate of the Sensor Unit. This opening will have to be oriented towards the Sun prior to each solar occultation observation. This opening can be closed by a mechanical shutter. Apertures definition: apertures Nadir face ( perpendicular to Zb) UV 42 x 45 mm2 IR diameter 32 mm aperture in (-Yb,-Xb) at 60 deg from -Yb diameter 2 mm (UV and IR Sun occultation) The Sensor Unit is located in the payload compartment of the S/C, near the -Y wall. A hole in the instrument mounting wall and in the -Y wall will be used for Solar occultation. Axis reference are in respect with Spacecraft Reference Frame (Spacecraft MICD, mechanical frame). Summary of operations: nI Operational Mode Target Subsystem Aperture -- ---------------- ------ --------- -------- 1 Test Mode NA NA 2 Sun Mode Sun UV+IR Secondary UV+IR aperture 3 Star Mode Star UV aperture on Nadir face 4 Nadir Mode Nadir UV+IR apertures on Nadir face 5 Limb Mode Limb UV aperture on Nadir face Pointing, general assumptions: Assume pointing is done by Spacecraft Assume rotation of 90 deg, duration is around 11 mn (0.14 deg/s TBC). It seems that Spicam is quite demanding concerning S/C manoeuvers and resources availability. We examine resources needed by Spicam: - Manoeuver duration: is dependent on orbit parameters, actual Spacecraft attitude and desired inertial direction (selected objective) and will computed. It may be that total manoeuver duration during one orbit may be in conflict with Earth attitude needed for data transmission. However we note that there are 2 orbits (of 3) per day without transmission to earth. - Other resources as wheel usage and power: Wheel usage is a resource to be shared between instruments. Nadir pointing is more wheel consuming than fixed inertial attitude. Power is not a concern for Sun occultation (it drops to 0 anyway). For Star occultation, the angle around +Z axis is a free parameter and therefore can be adjusted for maximum power collection if necessary. In the Inertial mode, pointing direction is any inertial (relative to stars) direction. This direction must be kept fixed during observation duration of 2 to 8 mn. It is defined as any star direction which may be occulted by Mars in dark side of Planet. (see operational modes for details) In nadir mode, nominal nadir pointing (as other instruments) in bright side of Planet. The following table gives the Experiment viewing requirements for each objective. Objective FOV (*) FOV avoidance Pointing Duration Direction (typical) --------- ----------- ------------- --------- --------- Star 1 deg x 3 deg 15 deg x 15 deg Inertial STAR 2 to 8 mn (UV) (Sun) Sun slit NA Inertial SUN 2 to 8 mn (UV+IR) Nadir slit NA Marsocentric 30 mn (UV+IR) (Nadir) Limb slit 15 deg x 15 deg Inertial 2 to 8 mn (UV) (Sun) There is no illumination constraints for OFF mode of Spicam for sensor point of view (energy is spread by grating). For information, following present orbit, 30 mn at Nadir around pericenter is the duration on orbit where S/C altitude is < 800km. (*) Spicam fields of view: UV channel Full CCD 4 deg x 3 deg STAR mode no slit 1 deg x 3 deg, no vignetting Nadir, Limb slit 1.3 arc min x 3 deg Sun pinhole 2 arc min IR channel Nadir 1 deg circular Sun pinhole 2 arc min Subsystems: =========== List of elements of Sensor Unit: UV channel parabolic off axis mirror, focal length = 120 mm slit with two positions grating intensified CCD with electronics box IR AOTF channel --->Servitudes Unit: This block is made of two boards: power board, which provides individual power for UV and IR UV needs +5, +15, -15 V IR needs +5, +/-12, +/-15V Peltier cooler (UV and IR) 3.3 V The input 28V is coming from DPU where it is filtered. microprocessor board, this board controls: the two mechanisms, the IR switch on, the high voltage level (for UV channel) and retrieves 8 temperatures. --->UV detector Unit: The UV detector is made of 3 parts: a CCD camera with the head and two electronic boards (follow on of Mars96) an intensifier (Hamamatsu) with a 12 mm window which is coupled to the CCD by fibre optics a programmable high voltage (Hamamatsu) for the intensifier In the head, the CCD (TH 7863) is mounted on a one stage Peltier cooler for a delta T around 15 0C. The two electronic boards of the CCD camera are mechanically mounted on the servitudes boards. The CCD detector head is mounted in such a way that the columns are perpendicular to the baseplate of the Sensor Unit. The rows direction is the spectral dimension. The UV detector records a window of 5 rows allowing to have at the same time, in Star mode, the Star spectrum surrounded by the background spectra. The rows can be elementary pixels or binned pixels (binned columns). The nominal binning is between 4 and 8. The position of the rows is programmable. --->IR Channel Unit: The IR channel is made of an entrance lens, an AOTF crystal which acts as a negative filter, two (Hamamatsu) single pixels detectors (two polarisations) with their own Peltier cooler, and an electronic board. When the AOTF is powered (at a certain frequency), it selects a wavelength which goes up to the detectors. A full spectrum is then obtained by scanning the frequencies. The measurement is obtained by the difference between the AOTF on and off. --->DPU and flight software: The DPU is made of 3 boards: the power board which has 28V Interpoint filter modules for the whole instrument and provides 5V for the DPU itself (Interpoint module), the microprocessor board, based on a 80C32 chip, with Ram, Prom, Fifos as buffer for telemetry, and counters for time maintenance. the interface board which has an Actel FPGA RH1020 for telecommand/ telemetry logic and interfaces circuits to S/C lignes. The DPU has two connectors for data lignes (one nominal and one redundant), two connectors for power lines, and one connector towards the Sensor Unit. DPU Hardware and software characteristics: microprocessor 80C32 30 MHz Eprom 32 Ko Ram 128 Ko for 2 pages Fifo TC 32 x 8 Kbits Fifo TM 3 x 32 x 8 Kbits (able to store 16 sec of data) Software code 26 Ko External data 43 Ko CPU load < 50 % Principal Investigator ====================== Jean-Loup Bertaux Service d'Aeronomie, IPSL/CNRS, FRANCE