ISS MER Status 1 June 2001 (from Felicity Vol. 62)
Excerpt from: 1 June 2001: Felicity Vol. 062 (2 MB Acrobat)
Problem Title | Problem Description | Current Status |
| C& C MDM Failures | Multiple C& C MDM failures. | All three C& C MDMs have functional MSDs loaded for 7A. C& C 3 – PRI, C& C 2 – B/ U, C& C 1 – STBY. Approx. 151/ 14: 10 GMT (9: 10AM Thurs. 5/ 31) there was a “MSD Inaccessible” flag set on C& C 3. |
| 4B BGA High Torque | BGA 4B showed motor torque values reached an average of 270 in- lbs during a four minute interval while performing nominal rotation for power- charging. During this interval, a maximum torque of 320 in- lbs was recorded. |
4B will stay in directed position mode. Team is investigating flying a replacement BMRRM on a future flight (7A. 1). |
| BGA 2B Current Spikes | Higher than expected BGA motor drive currents (up to 0.6A) during rotation. |
On- orbit data indicates that baseline 2B BGA motor currents are not increasing over time, but current spikes are increasing in magnitude and frequency. An open loop test has been conducted and the results are under analysis. |
| N1- 3B- A RPC 16 Trip | RPC feeding Node Smoke detector tripped unexpectedly after performing maintenance on the adjacent HEPA filter |
Power on of smoke detector for 2 sec. to detect a short was done with no short indicated. Additional T/ S planned. |
| Ku- Band Gimbal Temperatures |
Ku- Band gimbal temperatures repeatedly drop below certification limits. |
Team is investigating the feasibility of adding thermal blankets or adhesive heaters to the Cross- Elevation gimbal on a future EVA. |
| MCA Electrometer Op PBIT |
MCA unexpectedly shuts down | Intermittent shut- downs continue. Plan to R& R unit before 7A. |
| MCOR Overtemp | MCOR shutdown due to overtemp | The MCOR was manually shut down during its early operation when it exceeded 40 degc. The MCOR ART is evaluating the 40 degc operational limit, and will propose a software change to increase this limit to possibly 47 degc. |
| Possible Lab Window Contamination | Lab window cover was left open during Soyuz docking resulting in potential contamination from the Soyuz RCS jets. | Procedure is in place to establish rules for closure in order to minimize accummulated contaminants for all flights. A special rule has been drafted for the 7A mission. |
| ECOMM Connector FOD | During ECOMM antenna removal from the Node 1 Stbd port (EVA 2), a wing nut (approx. 2.5 inches) came off of one of the connectors. This connector was attached to the hatch ECOMM plate. FOD suspected from this wing nut is a total of three items. |
Crew will monitor CBM operations during 7A. The hatch will also be moved to the Test position during 7A before the EVA to determine if any hatch repairs must be made before Airlock berthing operaqtions. |
| Redundant String ACU (Arm Computer Unit) Brake Voltage Errors During Brake Release | Received Alarms: “R3B – SSRMS ACU DPRT Brk Switch Fail”, “R3B – SSRMS ACU DPRT Brk Voltage Fail”, “R3B – SSRMS Brk Voltage Err”. The alarms occurred during the extended jont range test, while in redundant string. The SSRMS safed automatically. | The failure has not recurred and troubleshooting has failed to reproduce the problem. Anomaly resolution team investigation is on- going with no clear cause of the problem being identified. |
| Shoulder Pitch JEU Anomally | Received R3C SSRMS SP JEU Transmit and Receive Errors while SSRMS operational on redundant string, but not being used. JEU was rebooted, and failure was reanunciated | The failure has persisted since the original occurrence. Troubleshooting is ongoing and has narrowed the list of possible failures to the Arm Control Unit or the Shoulder Pitch joint. Diagnostic software is being developed to characterize the events that led to the failure. |
| Unable to evacuate CDRA CO2 bed | After sucessful R& R of the CDRA Airsave pump, the CDRA was unable to pump down the AD/ DES 1 bed. |
Has operated in single- bed mode successfully. Replacement check valve is available on- orbit, but replacement plan is still being established (valve is not designed to be an ORU). |
| CMG Loss of Attitude Control | During operations to swap from US C& C2 to C& C3, TsUP commanded communication to be broken on the busses between the SMCC and the US C& C. Because the SMCC had no communication with the US C& C, the RS then started a timer (5 minute default) after which time they unconditionally took control. This led to a 3 minute force fight, after which the US CMGs reached saturation, and the US GN& C declared loss of attitude control |
After discussions between US and Russian engineers the situation is understood. The area of investigation focuses on why TsUP thought it necessary to inhibit higher bus communication and why autohandover was not inhibited since this is a planned response to the communication interuption. |
| CMG 2 Survival Heater Activation | CMG 2 spin bearing temperatures began to rise unexpectedly. The termperatures went from about 27 deg C to about 43 deg C within 6 hours. This temperature increase was attributed to the CMG survival heater coming on, so the RPC to the survival heater was opened, and the temperatures immediately began to decrease. |
Analysis of data indicates that the survival heater performed nominally for the given thermal environment (powered on due to decreased temp from being in shade). The behavior also matched thermal predict for this case. Predicts also show that the heater would have cycled off had the RPC not been opened. |
| ESP Survival Heaters Off since 6A | Power was removed from the ESP- 1 primary and secondary heaters during the 6A mission and they were left off until it was discovered approximately 30 days later. ESP- 1 houses a spare PFCS and a spare DSCU. |
A procedural error. Investigation into what caused it and how to keep it from happening again is underway. |
| SSRMS Anomalies | Check- out operations on the redundant string have indicated a problem with either the ACU, the JEU (for the shoulder pitch joint), or the connections in between. |
An ART is in the process of identifying further trouble- shooting tests. In parallel, wrok is underway to prepare for the potential requirement to change- out either of the ORUs on a future flight, ir required. |
| BGA High Current | BGA 4B has indicated high current during rotation and movement. |
The ART is working to determine the root cause and potential action. Testing has been conducted on both 4B and 2B to further characterize system performance. Power generation and loads are also being analyze to ensure ade quate margins for assembly missions and free- flight. |
