Aqua Daily Report May 20, 2002 1130 GMT – May 21, 2002 1130 GMT

(DOY 140:1130z – 141:1130z)

The following activities were completed:

1. At approximately 17:50z, we acquired the Earth. Subsequently, we transitioned to Earth Point Mode (EPM) and recovered to safe state.
2. Re-activated the Ultra-Stable Oscillators (USOs) and performed time jams and clock adjusts.
3. Uplinked the daily Master Command Loads and Ephemeris.
4. Began instrument recovery activities, including:
   1. AIRS to Standby/Startup
   2. AIRS to Standby/Instrument Initialization
   3. AIRS Decontaminate heater on
   4. CERES Fore power on
   5. CERES Aft power on
   6. Enable CERES science transactions
   7. CERES Fore/Aft diagnostic memory patch/dump
   8. CERES TMON activation
   9. CERES to safe mode

The following activities are scheduled for the next 24 hours:

1. Uplink an updated STA alignment patch (star tracker flight software alignment constants were updated to reflect corrected TRW matrices with Flight Dynamics calibrations applied).
2. Transition back to Fine Point Mode (FPM).
3. Uplink the daily Master Command Loads and Ephemeris.
4. Continue with instrument recovery activities, including:
   1. AMSU-A1 and A2 Activation
   2. HSB Power On
   3. AIRS to Standby/Cooler Off
   4. AIRS Memory Dump
   5. AIRS Warm Functional Checkout (Part 1)

Aqua Spacecraft Status:

1. Spacecraft State is currently Safe.
2. GNC Mode is Earth Point Mode, HiFi Ephemeris.

Aqua Instrument Status:

1. AIRS is in Standby state, Quiet bus is OFF, Noisy bus is OFF, Cryocooler is OFF with the Heater ON, Scan mirror rotating is OFF and earth shield is CLOSED.
2. AMSR-E is in Modified Sleep mode, rotating at 4 RPM.
3. AMSU A1 is in Survival mode and the antenna is in the Target position.
4. AMSU A2 is in Survival mode and the antenna is in the Target position.
5. CERES Aft is in Safe mode and the covers are CLOSED.
6. CERES Fore is in Safe mode and the covers are CLOSED.
7. HSB is in Survival mode and the antenna is in the Target position.
8. MODIS is in Survival mode, Nadir Door is Unlatched and CLOSED, Solar Diffuser Door is Unlatched and CLOSED, and the Space View Door is Unlatched and CLOSED.

Activities Deferred:

1. All further activities have been postponed until Spacecraft recovery to Fine Point Mode.

Anomalies:

1. A preliminary investigation of the DOY 139 16:09:42z transition to Survival state has been conducted. The recorded data shows the sum of the 12 Array Regulator Module (ARM) input currents rise from 0 amps at 16:09:22z while the spacecraft was still in umbra. The ARM inputs currents continued to rise, crossing the flight software’s “Eclipse Exit Threshold” of 1 amp at 16:09:26z. After peaking below 2 amps, the ARM input currents then decreased below the “Eclipse Entry Threshold”, also at 1 amp, at 16:09:32z. The spacecraft actually exited the umbra at 16:09:42z. The persistence of the ARM input currents levels, the first above and then below the thresholds, was sufficient to cause the flight software to interpret an eclipse exit and then an eclipse entry respectively. The flight software interpretation of eclipse entry combined with the DOD level of 13% resulted in the setting of the “Excess DOD at Eclipse Entry” level 3 fault flag. The preliminary investigation has focused on possible causes of the ARM input current behavior. Solar array clocking appears to be nominal up through the setting of the fault flag. Spacecraft attitude motion was not significant enough to produce the observed effect on ARM current. All 12 independent ARM currents behaved similarly, indicating this is not an individual ARM problem. The flight software processing of the ARM input currents is consistent with the analog telemetry points for all 12 ARMs. Investigation into possible hardware or software causes is continuing. External environmental effects are also under consideration. Similar ARM input current production in umbra has been observed in other orbits. Terra has also experienced solar array current production in umbra. The subsequent dip in current level, however, has not been observed in other orbits or on Terra in the data examined to date. Analysis of possible atmospheric causes is underway. The Electrical Power Subsystem has exhibited nominal state of health since the anomaly.