Solar-B E I S * EUV  Imaging  Spectrometer

Minutes of the Solar-B mission kick-off meeting ISAS, 8-13 March 1999 EIS instrument sections

half way	Contents General  Mission (plenary) sessions  EIS (splinter) sessions  Open Items and Actions      Open Items      New Actions      Closed Actions  List of Materials Future Activities  General The planned Japanese solar physics space mission, Solar-B, was the subject of this "kick-off" meeting, held at ISAS headquarters in Japan during March 8-13 1999.  This was the first meeting at which all the instrument teams were present (following the selection of US partners by ISAS, NASA and PPARC) together with Japanese scientists - from ISAS, NAO and elsewhere; as well as staff of the main spacecraft integration contractors.  Each of the three instrument teams held separate meetings. There were also some joint sessions involving more than one instrument group and plenary meetings involving all participants.  These notes describe the meetings which involved the EUV Imaging Spectrometer (EIS) team. Some notes of the plenary sessions are also included.  Mission (plenary) sessions EIS (splinter) sessions Notes.   criterion for low-maintenance instrument will be included in Management Plan. Noted that since the MTM/TTM testing was reported (by MELCO engineers) to be essentially in series, the EIS team will aim to provide test hardware that will satisfy both test requirements.Definition of Solar-B reference axes will be included in the EIS system interface control document. Noted existence of three documents which comprise the mechanical/structural interface standards. Standards for electrical design currently not available in English, but expected soon. Astro-E electrical design standards document will be made available as a guide. Noted reference to mathematical model instruction document per 5.3-3 of s/c overview. Information about need for application of contamination control measures must be conveyed to MELCO. Noted data regarding thermal design document. Mechanical Interfaces 1)   It was agreed that the mounting of EIS to the spacecraft would be with a leg structure, to be provided by the Solar-B spacecraft (MELCO) side, approximately as shown in p.'s 5.1-1 & 5.2-5 of the Spacecraft Overview presentation. Therefore the interface between EIS and the spacecraft will be between the -y ("bottom") face of the EIS and the attachment points on the Solar-B structural legs. There will be no additional legs attached to EIS in the flight configuration. 2)  The EIS instrument will be mechanically qualified, by BU, (for example by vibration test) with the instrument mounted on such legs and in the presence of a representative optical bench portion. The design may be additionally (or previously) evaluated when mounted on a fully kinematic mount but this will not constitute qualification. 3) At flight model, and possibly for other models (TBD), an exchange of templates between MELCO and BU will be used to control the mounting interface between EIS and the spacecraft. 4) Adjustment of the EIS alignment will be by shims (for rotation about the z and x axes) and by pin and slot for rotation about the y axis, with a TBD fixing method in the latter case. 5) Drawings of the interface will be exchanged. This process may iterate. Action item #46. BU to supply MELCO with a drawing of the immediate locations of the mounting points on the -y face of EIS.   Action Item #47. MELCO to supply BU with a drawing of the entire leg structure with all details necessary to permit its dynamical evaluation. 6) MELCO to provide the EIS team with a preliminary alignment procedure. 7) BU to provide MELCO with thermal interface information as requested by 31 March. 8) Action # 51. Mechanism motion characteristics will be supplied (at least in preliminary form) by end March 99, for frequently used items, as per the following table:     Item Mechanism Mass Torque (Max) Duration Time-dependence Duty Cycle 1 scan of primary Mirror           2 Slit exchange           3 slit focus           4 grating focus           5 shutter            Case studies will be shown in case of uncertainty in the designs, e.g. what if #5 comprises a filter section. Mechanisms with an extremely low frequency of use (e.g. door) need not be shown on this table. [MW notes: this information will be presented as a section in an EIS system interface control document]   Discussion on wavelength ranges  ... Electrical Interfaces Action 59: MSSL.Need to urgently re-state the EIS team preference for 28 V unregulated power with justification.    Action 60: MSSL+team.power budget estimates, with average and peak loads.  A further discussion took place on 15-16 March 99 with (MSSL) AJM, MW & (NAO) HH, Keiichi Matsuzaki Here are the notes as taken by Alec:   Requirements Review Pixel size: 1.9 arc-sec. Field of view: 4 x 4 arc min. Spectral Lines: 12 spectral lines should be adequate. Rasters: Normally would be sawtooth shape - progressive scan across the Sun with a fast flyback. An option would be to scan at the same rate in both directions, and reverse the order of the data in alternate scans. Advantages: minimise the disturbance torque. Disadvantages: possible inconsistent time progression compared to existing data sets. Exposure Times: Quiet Sun: predict about 10s. Active region: predict about 1s. Flares: possibly as short as 1ms. First part of flare is the most interesting. Automatic Exposure Control (AEC): Existing (Solar-A SXT) techniques look at the level of flux present two exposures before the current one to determine an auto exposure factor. An alternative approach is to look at the target a very short time before the required exposure - say 500ms before. To minimise the CCD readout time for the metering, one or two key lines could be chosen which are known to be active during flares. There is no need for the wells of the CCD to be more than partially full, in order to keep the metering time short, as maybe 20% accuracy is adequate. The sequence for AEC then becomes: Command to take exposure Short metering exposure Read two metering lines from CCD (no download to MDP) Calculate AEC factor in EIS Take real exposure using this AEC factor. Process data in EIS Download to MDP Typical Data Rates: SOT: 1 M pix per sec (~ 8 M bit per sec ?) XRT: 500 k pix per sec (~ 4 M bit per sec ?) EIS: 1 M bit per sec Likely cable run for EIS is 5m. (AJM: This is a significant length for data transmission and supply voltage losses. It definitely implies supply regulation in the camera head) There was a mantra repeated several times: CADENCE, CADENCE, CADENCE. Throughput is everything. If EIS carries out the data compression, it should include simple bit compression as one of a selection. Mission Data Processor This will be designed by NAOJ (KM) and built to contract. It connects the science and command channels of the three instruments to the spacecraft. For SOT? (XRT?) it provides all the processing power. Probably based on Thomson-CSF PowerPC 603e good to 60krad total dose. CCD Readout & Digitising Above 20 - 50kHz readout rate, noise increases with frequency. It might be possible to optimise the readout rate in a continuous manner with every exposure to give the lowest noise level. Timeline Setup ------ ------ Flush --- --- Exposure ------ Readout --- MDP Output Rate to Data Recorder 64kbit per sec average. Critical figure is 1 or 2 Mbit (TBD) per sec peak. We need to engineer the system, including the MDP, so that EIS (or any instrument) can take the full data stream for itself in case of other instruments being non-operational. Should physical maximum data rate of EIS be ~12Mbit per sec? (for drivers and cable) Need a way for EIS to estimate the data volume left at any point. Do this by MDP informing EIS at the start of the day of the available data space, and counting the data volume sent? Mission Uplink Very small data size, maybe three times Yohkoh (how much?). NAOJ to find value. Data corrected for tranmission errors (what bit error rate achievable?). Patches must be small! Some commands need tagging in their database as hazardous. Obvious examples are the door open and launch lock release. Observing Tables An important requirement for these is to minimise the data upload, probably with a system of pointers to tables already loaded in EIS. Necessary parameters include: Exposure duration Window Scan mode AEC parameter AEC enable / disable Dark / non-dark (?) Binning Slit Compression We should look at the use of SOHO-CDS to see what can be learnt. For Solar-A SXT, the major problem is that there is no timeline. EIS could also use a macro command structure, run with a parallel timeline to the observing tables timeline. EIS Thermal Control The spacecraft will be responsible for thermal control and monitoring of EIS. There are maybe ten channels for control and monitoring. Need to understand to what precision the spacecraft can control (NAOJ) and how many channels might be necessary with their requirements (BU). Non-operational mode monitors The door and launch lock status, and possibly other mechanisms, will require monitoring with EIS unpowered. This interface needs to be defined. Science and HK Packet Size Need to suggest maximum packet size - 10kbit first estimate. Is a compromise between too small giving a proportionally large overhead of framing data, and too large giving long retransmit times in the case of data downlink dropout. Estimated 20 packet per sec from MDP to DHU (data handling unit) using CCSDS format. EIS should use the same format if possible. Packets are fixed length header with variable length data, maximum length not defined. Main Bus Power Voltage not defined, but all three experiments prefer 28V. Inrush current, EMC levels, and most other parameters are not defined yet. 31 March meeting with MELCO will be important for this. Provide initial power budget with error bars for this meeting. ASTRO-E documents may help - Hara san to check. Shutter mechanism is likely to require 3W - same design as SOHO MDI. Design Principle A long discussion on user interaction produced the following concept: The system should be designed to be easy to use from a science user point of view, and should not inhibit any commands unless defined as hazardous. EGSE Nothing defined - CCSDS information will be basis for the format. ------------------- Actions (MSSL) Information requested from NAOJ: 61. What precision of temperature control can the spacecraft provide for thermal nodes on the EIS?   62. Define interface between non-operational mechanisms and spacecraft.   63. Peak data rate from MDP to Data Recorder for EIS. 64. (requested by MSSL) Total peak data rate from MDP to Data Recorder for all three instruments together. 65. Define general format and in particular the maximum length of packet from the MDP to DHU to allow EIS to consider use of the same format. 66. Outline concept of the interface between the Solar-B ground system and the EIS egse. Open Items and Actions Open Items  ... New Actions Arising  (action numbers continue from previous EIS consortium meetings)  46. BU - Supply MELCO (via H. Hara) a drawing of the spacecraft interface points on the -y face of EIS.  47. MELCO - Provide drawings and descriptions of the semi-kinematic attachment structure for EIS.  48. MELCO. Produce a preliminary alignment procedure  49. BU. Provide MELCO with thermal interface information as requested. 31/3.  50. NRL/MSSL. Mechanism motion characteristics table to MELCO.  51. All EIS team institutes. Provide data of materials proposed for use in, or in the vicinity of, the instrument optical components.  52. MSSL to coordinate update of mass and power budgets.  53. All. Select wavelength ranges.  54. All. State scientific objectives and requirements.  55. MSSL. Provide a statement of the need for contamination control hardware on the spacecraft (i.e. purge harness) on the spacecraft and up to launch.  56. hh/jd. Continue to develop and report the Hitachi-ruled SVLS gratings.  57. jd. Provide some SERTS spectra to MSSL for instrument (CCD) simulation and development.  58. BU/NRL. Implement a test programme of Cycom 5575 and/or other carbon-composite materials with appropriate multilayer coated witness samples.  59. MSSL: state main bus power preference 60. MSSL/team: power consumption estimates 61. MSSL/team: spacecraft heater/sensor requirements 62. MSSL/team: non-operational status items 63. MSSL: EIS peak data output rate 64. NAO: MDP/DR peak data input capacity 65. MSSL: EIS packet format 66. MSSL: ground system/EGSE interface concept. Closed Actions from previous meetings  List of Materials Session   p=plenary   e=EIS   x=XRT Title (or Theme)  Pages [slides] Author or (Presenter) Reference (MWT's system) p Agenda  11 Kosugi ko/m/0-2   List of Foreign Participants 1 Kosugi ko/m/0-1   International cooperation in the Yokhoh Programme  8 Kosugi ko/m/2   (Scientific Objectives etc.)  4 Kosugi ko/m/1   Master Schedule  1 Kosugi ko/m/4   Spacecraft Overview - SLB-M-E-99002  43 MELCO ko/m/3   Electrical Interfaces  1 MELCO ko/m/3-1   Requirements for structural mathematical models  8 MELCO ko/m/10   Mechanical Design Standards 13 MELCO ko/m/11   Contamination Control Program Plan  5 MELCO ko/m/9   Environmental Conditions for Solar-B  18 MELCO ko/m/8             Telemetry and Commands 8 Sakao ko/m/5   Attitude Control Systen  [16] Ichimoto ko/m/6   Data Coalignment Concept --> MDP -> Operations  10 Shimizu ko/m/7           e Observations with Baseline EIS   Hara ko/e/1   Thoughts on reaching closure ...   Mariska ko/e/2   EIS Structural Analysis   Mahmoud ko/e/3           x  XRT Mirror and Filter Performance  35 [69]  deLuca  ko/x/1    XRT Analysis Filters  [~16]  Kano  ko/x/2   XRT Engineering Presentation 36 Cheimets  ko/x/5   CCD Charge spreading 9 (Bruner)  ko/x/3   CCD test for device selection [14]  Kano  ko/x/4 Future Activities