RHESSI Tohban report, 11-June-2008 to 18-June-2008
Gordon Hurford (ghurford@ssl.berkeley.edu)

1. Solar Activity

The Sun was very quiet this week, with the largest event having a GOES level of A5.

2. Memory Management

Satisfactory.  Memory usage was brought down to zero each day after peaking at 20-25%.

4. Offpointing operations

On 12-June the software patch was uploaded to support offpointing operations.  RHESSI was also spun down to 14 rpm.  This
rotation rate (as opposed to 15 rpm) should remove remove the degeneracy in the FSS aspect data whose sampling interval of
10.0 seconds corresponds to sampling every 2.50 rotations at 15 rpm and 2.333 rotations at 14 rpm.  The goals of this
year's Crab offpointing operations are twofold: first to obtain mapping data with the resulting improved FSS aspect
solution; second to use fan-beam modulation to cross-compare spatially-integrated Crab spectra for each detector.  This
technique is insensitive to background subtraction and to the fine details of the aspect solution and should be able to
establish the relative sensitivity of the detectors at low energies.

Offpointing began on 13-June at 04:20 UT when the Crab was 2.1 degrees from the Sun with 3 OFFPOINTING/IDL command
sequences, followed with one more on 14-June and two more on 16 June.   The roll predictions and commanded offpointed
trajectories were quite satisfactory. Although the ACS system was IDLEd after each offpointing orbit, 'inertial' spinning
still resulted in a consistent drift of unknown origin of about 0.3 degrees per day to the WSW.  Such drifts have been
observed in previous years although the direction varies from year to year.

As of 18 June, three potentially useful intervals of Crab offpointing data had been obtained:
13-June 09:15 to 14-June 04:17
14-June 05:49 to 16-June 02:31
16-June 07-25 to present

During these intervals the s/c offset to the Crab varied from 0.5 to 0.7 degrees, 0.15 to 0.6 degrees and 0.4 to 0.1 to
>0.6 degrees.
Detailed trajectories relative to the Crab can be found at
http://sprg.ssl.berkeley.edu/~mfivian/crab/20080612/abs_coord20080620.png
and subsequent URL's.

Since the mapping objective requires offsets of ~0.1 to ~0.5 and the calibration requires offsets greater than 0.4
degrees, the current plan is to let the drift gradually increase the offset from the Crab to provide additional
calibration data.

4. Data Gaps

There were several gaps in the Monitor Rate, SOH and PMTRAS VC1 data on June 11-14, with the largest being about 20
minutes.  Details are given below.

GAPS IN APP_ID = 102 (VC3-MONITOR RATES) WITH PACKET RATE LT 30
GAP START TIME              GAP END TIME                   GAP (SEC)
2008-06-11T19:50:00.000 -- 2008-06-11T19:55:00.000       300.00000
2008-06-12T04:55:00.000 -- 2008-06-12T05:10:00.000       900.00000
2008-06-12T05:25:00.000 -- 2008-06-12T05:30:00.000       300.00000
2008-06-12T05:35:00.000 -- 2008-06-12T05:55:00.000       1200.0000
2008-06-14T02:35:00.000 -- 2008-06-14T02:40:00.000       300.00000

GAPS IN APP_ID = 154 (VC1-PMTRAS) WITH PACKET RATE LT 4
GAP START TIME              GAP END TIME                   GAP (SEC)
2008-06-12T06:00:00.000 -- 2008-06-12T06:05:00.000       300.00000
2008-06-13T17:35:00.000 -- 2008-06-13T17:55:00.000       1200.0000

GAPS IN APP_ID = 1 (VC1-SOH) WITH PACKET RATE LT 30
GAP START TIME              GAP END TIME                   GAP (SEC)
2008-06-13T12:00:00.000 -- 2008-06-13T12:10:00.000       600.00000

5. Next Tohban: Martin Fivian