ACE Leonid Readiness -------------------- All Spacecraft subsystems will remain on and in their nominal state during the storm. The spacecraft will be reoriented to ~106 deg from Leonid radiant on Nov 16 (prior to the storm peak), for optimal shielding of science instruments. An attitude maneuver on Nov 18 will return the spacecraft to normal operations. Some science instruments will be reconfigured several days prior to the storm peak: - SWEPAM-E and SWEPAM-I - Disable HV power supplies - SEPICA - 30KV HV power supply off - SWICS and SWIMS - Disable and safe HV power supplies - ULEIS - HV off and shutter closed CRIS, SIS, S3DPU, EPAM and MAG will remain in their nominal states. The low-rate broad beam antenna will be used during the reorientation, so there will be no data recorder operations. Some science data loss (for the instruments still in their nominal state) may result. There will be 8 hour DSN support during the storm peak. During that time, the FOT will be staffed with 3 experienced console personnel and additional monitoring will be done by other FOT members on backup consoles. A representative of the spacecraft manufacturer (JHU/APL) will also be present. Contingency procedures are ready and are being tested. SEPICA Status ------------- Beginning on 11/9/98, the Sepica Fan 2 pressure declined over a period of two days from the usual 24 torr to 5 torr, which is too low for operation. Fan 3 remained in a nominal condition. The leakdown rate was consistent with either a slowly closing fill valve, or a new leak in the windows. For nine months, the Fan 2 fill valve has been resting slightly ajar. It has allowed gas to continuously enter the proportional counter and its leak orifice at a stable pressure of 24 torr. This smooth regulation arose when the metal properties of the valve changed after several months of operation in flight. In the past, the fill valve of the companion Fan 3 has closed spontaneously from a partially open to fully closed state. As in this case, the counter is emptied if active gas regulation is off. A refill of Fan 2 will show whether the valve has simply closed, or if a window has a new leak. This test will have to be taken up after the Leonids have passed. S3DPU Status ------------ Substantial progress has been made on the problem of S3DPU resets. The microprocessor tracing equipment that was set up at UNH has allowed the design engineer in Germany to identify a subtle software bug that causes the EM S3DPU to reset. This EM S3DPU is being tested while connected to a spare SEPICA sensor fan, and the resets seem to occur only with SEPICA in one particular operating configuration called Engineering mode. A patch has been developed to handle this, and it is currently being tested. Meanwhile, the flight S3DPU has operated without reset now (and with SEPICA NOT in Engineering mode) for over 40 days, the longest period since early July.