Meeting: Team Engineering Meeting

Doc ID: EIS-meet-cons-EM9911-minutes

Issue: 1

Author: APD

Date: 11 December 99 – 14 December 99

Location: ISAS Japan

Those Present were representatives from:
NRL, NASA, BU, MSSL, ISAS, MELCO and MHI.

Tetsuya Watanabe extended a warm welcome to everyone and thanked all participants for attending on a Saturday. Len Culhane gave a brief overview of the project and Tony Dibbens summarized the project schedule.

Melco described the status of the spacecraft programme and identified that the design schedule was on target. Melco had prepared an EIS thermal model and a thermal analysis had been performed.

George Simnet showed a schedule for BU’s composite development programme and Saad described the position of EIS on the spacecraft and the envelope constraints given by Melco.

A description of the mechanical design was then presented. The Clamshell was shown to be on the Strongbox. Thermal reflection from the aluminium still needs to be checked. There will be no front door and the Clamshell doors will be one shot devices. The outer door actuator needs to outside the current instrument envelope and consideration will have to be given to shielding it from direct sunlight.

There may be problems with the MHC Box being in the light path.

Details of the actuator mechanism were shown and it was confirmed that limit switches would be required.

The current plan is not to use a launch lock.

A template for the mechanical interface will be required by Mar/Apr/ 2001. Melco asked for an optical alignment cube on this template. EIS should define where this should be.

Melco described the alignment concept for EIS.

Saad to send CAD file of template to Melco for their comments on thickness/stiffness and position of alignment cube (see Action 238). This alignment procedure was accepted as fine in principle, but just needs some further details.

The accuracy of instrument co-alignment was discussed.

The base of the Strongbox would be made of honey-comb material which could be either aluminium or carbon fibre composite. Inserts will be fitted into the honeycomb base to support the boxes. These inserts will probably be titanium, or could be composite. Aluminium inserts could be used in areas where optical assemblies are mounted, although the feet of the optical assemblies will mate with composite material.

Saad will make some specific requests for envelope changes (see Action 250).

Melco described the spacecraft system structure including the FEA of EIS supplied by Saad. When mounted, a 4Hz reduction in the lowest resonant frequency was demonstrated. The lowest frequency for the whole spacecraft was 23.6Hz. Excitation levels for the system analysis were given. The current resonant frequencies for EIS were acceptable to Melco.

Sub-system test characteristics (vibration and acoustic) should be available form Melco in about 2 months (see Action 240).

Melco will supply the mounting bolts and the reamers for the holes. Melco will also supply shear pins for a fit check prior to instrument delivery. Access to the mounting nuts should not be necessary for assembly.

The EIS sub-system load levels were shown in x, y and z. The sub-system load test will be conducted with EIS mounted on a test fixture fitted to its legs.

During a simulated random vibration the end of EIS moved 2mm. The final requirement for a launch lock will be decided after UK vibration tests on the MTM.

An updated structural math model is required by Melco if there is to be a launch lock. Saad to send 2 updated structural math model to Melco by April 2000, with and without the launch lock (Action 201). Spacecraft side will assume there is to be a launch lock and made the necessary provision.

BU will also provide interface details of the launch lock and details of its design in April together with the FEAs (Action 202). Any information that can be sent earlier would be much appreciated by Melco.

An MTM test plan was shown and ISAS agreed to supply a test flow for the mechanical/thermal testing (Action 203). If more than 3 monitoring devices are required during these tests, they will need to be supplied by EIS, complete with monitoring equipment.

Any modifications to the MTM to prepare it for the thermal tests, will be conducted by the EIS team in Japan.

EIS needs to prepare a draft ground handling procedure (Action 204). EIS will be attached to its mounting legs for the mechanical tests. The legs will already be attached to the jig. A lifting facility must be available on EIS to allow it to be attached to a counter balance.

Saad presented the thermal model of EIS. It had about 50 nodes. He also described some tests conducted at BU with a Peltier cooler. At power inputs of less than 10W there is some potential benefit to cooling the CCD.

Saad accepted that the thermal model format was not usable by Melco. BU could obtain the software to correct this but there would be some delay. However Saad said that he could easily explain how the existing information could be used.

ESA, Lockheed and NRL would be approached to see if they had the facility to translate Saad’s software (Action 205) and Saad was requested to obtain the necessary software to deliver a usable model (Action 206).

A splinter meeting was convened to talk to Melco thermal engineers.

The box will dissipate 18.8W average. The estimated foot print is now 340x235x100mm. Melco will investigate this by end of Jan 00 (Action 207). The ICU will need to be painted black. MSSL will prepare an ICD for this box (Action 208). J side will responsible for the thermal coupling of this box to the Spacecraft Bus.

Melco to advise on the magnetic flux that the ICU will see in its confirmed position (Action 209).

The operating temperature range for the ICU was suggested to be -20 to +55 degrees C and survival -30 to +65 degrees C. MSSL to confirm these (Action 210).

A description of the cable requirements between the EIS electronic boxes was given by AJM. The cable between the ICU and the EIS structure is to be supplied by Melco, however they requested to have the Space Wire cable supplied to them. D type connectors would be used everywhere except for the Space Wire link, where Micro Ds would be used.

Melco need to know the number and position of the survival heaters and HK monitors. The maximum survival heater power is 5W per channel. The EIS team will provide the survival heaters and thermistors (to be specified by Melco) and The EIS team will fit them. MSSL will clarify the heater requirements and provide pin-out details to Melco (Action 211). D type connectors will be used. Survival heaters and thermistors will be fitted to the MTM/TTM. The cable harness for these will be provided by Melco and the wiring on the structure will come to a common point to facilitate this.

There are 2 contamination engineers working on the contamination plan in the USA and together with Jim Lang, this should be available by the end of February.

Both molecular and particulate contamination will be monitored. Small witness optics will be placed near the mirror and grating, two per position. One will be capable of being removed periodically, whilst the other will be left to determine total dose. A transmittance test will be used to measure molecular contamination. Consideration should be given to having a third pair of witness optics near the CCDs.

The EIS instrument will always need to be kept in a very clean area.

It was suggested that repressurisation in a vacuum chamber should be done very slowly through the instrument purge lines. A word of warning was given by the NASA representatives on using the correct grade of purge gas.

Bake outs are planned at sub-assembly level and in its fully assembles state.

A red tagged cover will be used as an outer door for most of the ground based activities.

It was stated that a nasty out-gassing material is used in the nose cone of the rocket and consideration should be given to this.

Various considerations on both particulate and molecular contamination were presented, together with ideas for their control. Concern was expressed about the level of cleanliness in the ISAS cleanroom.

Melco explained the cleanliness situation in Japan and it was suggested that a clean test area be prepared within the cleanroom just to cover SolarB. The Japanese were not optimistic about being able to achieve this.

Information on purging and vacuum requirements on the rocket needs to be provided as a hole will be required in the fairing. The nitrogen purge connection type, flow and position on EIS needs to be identified (Action 212). The vacuum requirement is just for the filter inside the Clamshell and will only need a small supply line.

Saad (with help from CB) has prepared the necessary information for Melco. Melco’s thermal engineers will continue working on this for the next few days to confirm that they have all the information they need. The name and address of Melco’s thermal modeling supplier was given to Saad.

The spacecraft thermal analysis was presented by Melco.

ICU dissipation is 12 to 18W, depending on the operating mode and 0 to 1W in non-operating mode.

The predicted dissipation for the ICU is as follows:

ICU Structure

Off mode 1 0

Standby 10 15

Operation, average 19 18

Operation, peak 19 33

Peak power includes the operation of one mechanism.

These figures include the operational heaters.

Corrections were made to the length of the mirror end of EIS and to the position of the radiator in the Melco documentation.

Tables 3.1.1 and 3.1.2 in "Solar B Telescope Thermal Interface Condition" are provided as information to sub-systems to help with their analyses. EIS would like more accurate information in the vicinity of the EIS radiator to help with radiator modeling – this can come from the first run of the Melco thermal model (Action 213). Discussion about moving the Bus radiator close to EIS will be considered with the CCD radiator presentation on 14 December.

Melco presented the definition of co-alignment of the instruments, together with the co-alignment requirements. An explanation of how the errors are derived was given. A request of 1 arc second stability between EIS and SOT during one orbit was requested, but this was thought to be very difficult. The following two actions were suggested:

Contact the science community to see if the requirement for co-alignment can be relaxed (Action 214).

Calculate the orbital variation of pointing stability (Action 215).

An estimate of 1 arc second was provisionally allocated to the 4 contributing parts to the alignment error (SOT internal, SOT system, EIS internal, EIS system).

80 arc seconds, as the full operational requirement for DC offset was considered to be a very difficult requirement.

Measured values of CTE for carbon fibre composite will be e-mailed to Japan (Action 216).

A presentation about disturbance torques was given by Melco. A request for disturbance information in a specific format was made by Melco.

Charlie Brown then presented the moving parts of EIS together with the information required. A splinter group was convened to progress this further.

A description of this interface was presented by K Matsuzaki of ISAS.

The MDP does not need to monitor the vacuum within the Clamshell.

A detailed description and block diagram for the vacuum MGSE/EGSE for the Clamshell was requested (Action 217).

HH to provide a nominal schedule for the launch campaign (Action 218).

In the electrical circuit for the Discrete Command Diagram, concern was expressed about the impedance of the MDP drivers. The impedance of the twisted pair line will be about 100 Ohms and this could cause a problem. Solutions to this problem could be series termination or end termination.

Possible problems with shielded transmission lines were raised by Lockheed and a choke may need to be included to reduce common mode noise.

AJM to write notes on the twisted pair impedance situation and submit to Melco (Action 219).

HH to supply definition of status levels - SOT uses 3 types of status data (Action 220).

Rise and fall times for all the timing charts to be provided (Action 221).

AJM to write note on rise and fall times based on experiences from other missions (Action 222).

MSSL to advise on preference for one of the two Enable options (Action 223).

MSSL to talk to Dick Shine of Lockheed reference the type of data compression to use - to be resolved by the first quarter of 2000 (Action 224).

MSSL to look at the format of the header to see if it can conform to the ISAS proposal (Action 225).

AJM explained the details on the diagram with particular reference to the spacecraft interfaces. The 3 survival heater will be as follows: 1 circuit to warm the mirror and MHC box, 1 for the shutter and slit/slot mechanisms and the 3^rd for the ROE, CCDs and grating. This is the first and provisional attempt at their positions. Two of the nine temperature sensors would preferably be on the ICU with the remainder distributed about the instrument. All nine temperature sensors will be provided by Melco and they would prefer just one sensor on the ICU.

The length of the ICU to structure cable was reviewed. Consideration must be given to data signals and power voltage drop.

The flight cable is most likely to be between 5 and 7 metres long. The speed of signals on the IEEE 1355 line between the ICU and the camera is 20Mbit/sec. It would therefore be beneficial to locate the ICU as close as possible to the EIS structure. It was agreed in principle that 24 gauge wire would be acceptable for the Space-wire link. MSSL will check that it will fit the Micro D connector (Action 226). MSSL will send a data sheet for the IEEE 1355 drivers to Melco (Action 227).

After much discussion, it was agreed that MSSL would make the part of the flight cable consisting of the high speed data link (IEEE 1355), ICU to camera. This is most likely to be in 2 parts, making a total of 4 cables. They will be fitted by Melco.

In addition to the high speed link, the cable will have:

2 D types for the temperature sensors and the thermal control to the spacecraft,

1 D type for the command, data and status connections to the ICU from the MDP,

2 D types for the power and power control from ICU to MDP,

3 D types between MHC and ICU,

1 D type between camera and ICU,

The grounding philosophy for the structure and the ICU was discussed. MSSL agreed to provide a first draft of the electrical ICD by the end of Jan 00 (Action 228 – same as Action 208).

The power distribution and mass of components is required Melco (Action 229).

The power dissipation and typical power usage was described. The individual power budget file was requested by HH (Action 230).

A number of questions were tabled on electrical matters:

1. Can EIS use the Data Recorder as a circular buffer for use in flare detection? - No.
1. Can all clock frequencies be defined as integer divisions of a master clock? - Yes.

1.3 Can the science, command and status data interfaces be made the same at least at the hardware level? - MSSL can design similar lines for science and status data. Science line is not 16 bit.

2.3 What is the radiation specification? ISAS to provide radiation document to MSSL (Action 231).

2.4 Foot print for the ICU. See Action 207.

8.2 What is flux from the magneto torquer? It generates a maximum of 50Ampere turns/m. The flux that the ICU will see will be calculated (Action 232 – repeat of Action 209).

Other questions to be answered in a splinter group.

The operating concepts were presented by RAG.

It was suggested by ISAS that the proposed timetable for sequence commanding should reside in the DHU. It was agreed that this would be a good idea and MSSL would look at the practicality of doing this (Action 233). HH to provide data and time lag command descriptions from DHU (Action 234).

The following conclusions were drawn:

1. The speed of the primary mirror should be limited to 10 – 20% of the maximum motor speed to reduce its disturbance torque.

2. Fine scan is OK because of the mirror’s small moment of inertia about its own axis.

3. Need to avoid operations at frequencies of approximately 1Hz and 3Hz, because of possible interaction with the solar panels.

4. The focus adjustment of the grating may be a problem, because of its large radius from the spacecraft centre of mass.

The actions already noted were agreed and the following actions were additionally identified:

MHI to send common command formats for the status request commands and the memory uplink/downlink commands (Action 235 HH).

MSSL to provide justification for the EIS flare flag (Action 236 RAG).

Identify preference for mission packet transfer options (Action 237 RAG).

Submit CAD file for alignment template for review (Action 238 BU). CLOSED

Melco to provide EIS & NASA with acoustic levels and tolerances for launch (Action 239 HH).

Melco to decide on acoustic test levels and provide to EIS and NASA (Action 240 HH).

Melco to provide BU with mounting hole tolerances and a CAD file of the interface legs to EIS (Action 241 HH).

Send copy of environmental test specification to Melco (Action 242 NRL).

Advise MHI if MDP needs to retain the ability to use JPEG on EIS data (Action 243 NRL).

Propose a grounding scheme for EIS (Action 244 AJM).

Prepare the power budget for 26, 28 and 30V (Action 245 AJM).

System side to clarify voltage at which power calculations are made (Action 246 HH).

System side to identify how the MLI is to be grounded (Action 247 HH).

Confirm recalculations of disturbance torques (Action 248 NRL).

Send CAD file for current mechanical design to HH (Action 249 BU).

Define procedure for change request to EIS envelope (Action 250 APD).

They have checked the information provided by Saad and have requested a change to the model.

HH to talk to CB, Saad and Melco engineers in a further splinter group.

The design of the structure is going well. Currently the facilities are being organized and waiting for the autoclave delivery in mid February. Some sample manufacture and testing has been performed – joints and helicoil and carbon fibre inserts.

Aluminium honeycomb may give problems with out-gassing. Carbon fibre honeycomb is available, but is not space qualified. An aluminium honeycomb test piece will be made once the autoclave has arrived. Sealing of drilled edges will be essential. It was commented that stress relieving does occur when holes are drilled into CFRP skins. Consideration should be given to anti-peeling screws.

The central tube of the Clamshell will be machined out of solid. Its design is at the schematic stage at present and it will be fitted to the end of the central strong box. Detailed design work will start in January 00. CB explained about reflections from the aluminium filter, which could potentially heat up the inside of the front tube. He showed a diagram of scatter using a HeNe laser onto an aluminium filter.

From the EIS view point, the main purpose of the PM testing is to checkout the ICU – MDP interface.

Although it will be an early test, there will need to be some form of camera, albeit in a primitive form. An MHC simulator will be needed, but better fidelity would be good.

EIS will prepare an MDP simulator for development work and an updated interface between MDP and ICU will be needed to facilitate this.

The ICU – MDP is the priority for these tests, mechanism and camera interfaces will be included if they are ready.

RAG presented general goals for the onboard software for these tests.

A presentation was given by CB, including a report from Swales Aerospace.

WTO presented information provided by Dynatherm.

Very similar results were obtained by both analyses, cooling the CCD down to –50 degrees C.

A mass penalty of approximately 1kg would be involved and space at the end of the EIS telescope would need to be allocated for the radiator.

Saad stated that a radiator at the end would be expensive and that it would definitely require a launch lock to be fitted. He was not convinced that the Swales and Dynatherm information was consistent with the XRT radiator information and suggested that D Tye’s work be revisited with better information from Melco.

WTO to calculate the parasitic load into the CCDs from the camera head (Action 251).

Saad to calculate the radiator temperatures for the baseline radiator configuration (Action 252).

NRL to review CJM’s work on CCD recommended temperature range (Action 253).

Note: HH to provide more accurate temperatures in the vicinity of the radiator – earlier action 213.

CJM presented data on the CTE tests conducted to date and also a summary of the camera design.

AJM gave a brief overview of the MHC.

CJK gave a presentation on NRL’s contribution to the MHC. They will provide designs of controllers for all the mechanisms, complete with software, with the exception of the piezo actuator. For the PM NRL will provide the electronic hardware. MSSL will provide the power supply/conditioning and deal with the temperature sensors and heater controllers and the box for the PM. The flight model will be built by MSSL.

The question was raised as to what should EIS do when passing through radiation belts? (Action 254).

NRL to clarify the support required for the NASA review (Action 255).

MSSL to review possible PDR for the EIS instrument (Action 256).

A telephone call will be initiated between MSSL and ISAS at 09.00 UK time every two weeks (Action 257).

TBA