Roman Space Telescope RFP Questions.pdf

Roman Space Telescope RFP Questions #1:

Question #1: 1.3.1 We are missing all documents except for 2231111

Response: The specified ICDs were not ready in time for the RFP and the ones provided include the best info that is currently available for the panel dimensions and stay out areas. Proposing to these ICDs will be sufficient for evaluating the initial design.

Question #2: 3.1.5.1.(a) Refers to 1.3.1, we don’t have the documents to review.

Response: Addressed in Q1.

Question #3: 3.1.7.(e) Can the diode locations indicated in the ICD be moved?

Response: Yes, there is no strict location requirement for the diode locations other than to be grouped into a single location per panel. And a preference that they be near a stay out zone or panel edge to reduce some of the lateral heating from surrounding solar cells.

Question #4: 3.1.7.(f) Can the OSR locations indicated on the ICS be moved?

Response: Similar to the diode boards there is no strict location requirement but must be co-located opposite the diode boards to provide the cooling necessary for their derated temperature.

Question #5: 3.1.7(g) –Notes that blocking diodes must be <125C with a panel temp of 136C. For the body-mount panels, the back-side blocking diodes would be radiating to a hot spacecraft, if MLI is to be applied over the diodes then they will not radiate to space. This requirement may not be possible to be met, please clarify if we are misunderstanding.

Response: The panel backs will be covered in MLI so there is no heat escape path for the diodes from the back, therefore the requirement to locate OSRs on the front of the panel opposite the diode boards is necessary to reduce and reject enough heat to meet the temperature requirement. 136C is the expected peak temperature of the solar cell areas and not the OSR area.

Question #6: 3.1.7(g) – specifies that the back facesheet will be covered in MLI. Will the MLI be applied to the CFE substrate before it is supplied or is the MLI the responsibility of the Contractor?

Response: The MLI will be applied by NASA after the completed panels are delivered.

Question #7: 3.1.8.(d) Are the “critical areas” all section wiring? Is this only applicable if there isn’t another rigid insulator between the wire and back face sheet?

Response: The critical wiring is considered the wires carrying the full circuit currents (i.e. after strings are combined into segments), not the wiring for individual strings. Anywhere these critical wires are run will need additional insulation between the wire and the back facesheet. The rationale is due to the added risk of the MLI potentially rubbing on the wires which may damage the insulation enough to expose it to potential shorts to the substrate. If there is another insulator between the wire and the back facesheet in some areas, this would be sufficient without adding additional insulation in those areas.

Question #8: 3.1.8.1 – discusses a Core Sun Sensor. Is the Contractor providing the CSSs or just the wiring? Will the substrates come with the CSSs? If the contractor is providing the CSSs, what are the requirements for them?

Response: The contractor is only responsible for providing the wiring for the CSSs. The CSSs will be installed by NASA after the panels have been delivered.

Question #9: 3.1.8.2 – discusses a monitor cell. Is the monitor cell to be CFE, or is the Contractor providing this? If the Contract is to provide the monitor cell, what are the requirements for it?

Response: The contractor is to install the monitor cells and they are wired in a similar fashion to other signal wires such as the PRTs (i.e. a single cell with wires that go directly to the signal connector). It is meant to be used to measure the Isc and Voc of the cell by the RST power system to act as a sample cell for the purpose of tracking the degradation of the solar array over the life of the mission.

Question #10: 3.1.9(g) through (o) – describes the required circuit wire redundancy. Can NASA provide some explanation for up to 8X redundancy? Does this mean 8 wires per segment as a group of strings or section as all of the sections together? Does this include primary and redundant wires or just primary?

Response: The number of wires is per segment once all the strings for that circuit are combined into a circuit and will be split between the primary and redundant wiring. For example, in section g) it asks for 8 pairs of wires for the PWM segment so when split into primary and redundant wires, 4 pairs will go with the primary and 4 pairs will go with the redundant harness. Similarly for the Digital segments, 4 pairs total per segment but will be split 2 pairs on primary and 2 pair redundant.

Question #11: 3.1.9.(h) Does this mean 4 wires per segment as a group of strings or section as all of the sections together? Does this include primary and redundant wires or just primary?

Response: As described for Q10

Question #12: 3.1.9.(i) Does this mean 4 wires per segment as a group of strings or section as all of the sections together? Does this include primary and redundant wires or just primary? o 3.1.9.(k) Does this include primary and redundant wires or just primary?

Response: As described for Q10, all wire counts include primary and redundant wiring and are intended to be split as such.

Question #13: 3.1.9(k) – is the hinge damper heater provided as part of the CFE substrate? If not, what are the requirements for the heater?

Response: The contractor is only responsible for providing the wiring for the damper heaters, which include primary and redundant (2 pair total). The damper heater will be installed by NASA after the panels have been delivered.

Question #14: 3.1.9(l) –is the potentiometer provided as part of the CFE substrate? If not, what are the requirements for it? o 3.1.9.l Does this include primary and redundant wires or just primary?

Response: Same as described for Q13.

Question #15: 3.1.9(m) – is the thermostat provided as part of the CFE substrate? If not, what are the requirements for it?

Question #16: 3.1.9.(m) Does this include primary and redundant wires or just primary?

Question #17: 3.1.9.(n) Does the redundancy requirement not apply to the CSS wiring?

Response: There is no additional redundant wiring for the CSSs. The redundancy is provided by the multiple CSS units that will be installed by NASA.

Question #18: 3.1.9.(o) Does the redundancy requirement not apply to the PRT wiring?

Response: There is no additional redundant wiring for the PRTs. The redundancy is provided by the multiple PRTs to be installed on the panels by the contractor.

Question #19: 3.1.9(i) – Does this imply that the unswitched segment is to be split in two sub-segments, such that 2 strings are in parallel on Panel 3 and 2 strings are in parallel on Panel 4?

Response: The unswitched segment is split into 2 strings each on panels 3 and 4, but are not combined across panels into a single segment. For the purposes of wiring, they can be treated as 2 separate circuits since they come from separate harnesses off of separate panels. So each sub-segment will combine the two strings at the diode board with 2 pairs of wires (1 pair primary, 1 pair redundant) coming off each panel harness. The sub-segments will eventually be combined at the RST power system level.

Question #20: 3.1.14 – only a charged proton spectrum has been provided. Can the Contractor assume that the contribution of charged electrons is negligible? Also, the proton spectrum is provided under the

5.5.2 Total Ionizing Dose heading. Only TNID maters for solar cells, please confirm that TNID analysis can assume that only this proton spectrum (Table 5-3) should be used as input to the analysis (i.e. it fully captures the expected proton spectrum and electrons are negligible)?

Response: Yes, solar protons may be considered the primary source of degradation and Table 5-3 and 5- 4 may be used for that purpose depending on method used. Table 5-2 is meant to screen other EEE parts that are not solar cells that may be on the solar panels.

Question #21: 5.5.3 – withstanding a charging environment is noted, but no information on the expected ESD environment is provided. Can NASA please clarify what is expected?

Response: Internal analysis has indicated surface charging should not be a concern. No extra action is expected from the contractor to mitigate charging effects.