Monthly Observatory Report
for
June 1995
COSTAR:
The COSTAR Deployable Optical Bench (DOB) has been has not been moved during the reprting period. All engineering telemetry show nominal readings.
WFPCII:
WFPCII continues to operate nominally throughout the month of June.
UV throughput was restored following the 6 hours CCD decontamination on days 153 and 178 (see Figure F2).
Science and Calibration observations continued to execute successfully.
FOC:
FOC is continuing the normal science program with GO and GTO cycle 4 proposals using the f/96 relay without problems. For a picture of the Faint Object Camera click here.
FOC proposal 5526 " FOC UV Throughput Monitoring " has been successfully excecuted on day 154 to monitor effects of OTA desorbtion.
FOS:
The FOS continued to execute a variety of GO, GTO, and CAL proposals during the month of June.
On day 171 starting at 10:03 UTC, four FOS controlled dwell/peakup scans were scheduled. This was the 1st time a FOS controlled dwell/peakup has been scheduled with an actual science proposal. FOS dwell/peakup scans have traditionally been accomplished using DF224 canned scans. The FOS FSW would transmit the time of the brightest dwell via the NSSC-1 PIT and the DF224 would execute the slew to the brightest point. As part of the NSSC-1 5.3 FSW update the FOS FSW YFPKUP was updated to execute dwell/peakup scans by transmitting multiple type 59 slew via the NSSC-1 PIT. The primary rational for the change in method was to give the FOS the capability to execute a dwell/peakup scan on a moving target, a capability not provided by the old method. The initial review of the engineering telemetry indicates that all four Peakups scheduled on day 171 executed successfully.
GHRS:
Both side 1 and side 2 of the GHRS are running without problems.
1.2 Summary of major problems
COSTAR:
COSTAR operations during the reporting period was nominal. Electrical and thermal monitors of the Instrument continue to show nominal values.
FOC:
In general: No major problems with FOC operations during the reporting period. Electrical and thermal monitors of the Instrument continue to show nominal values.
An unusual swing in aftshroud temperature was noticed on day 175. The temperature deviation was caused by an OFF-nominal roll attitude of the scacecraft followed by a long High Voltage ON period. While the OFF-nominal roll attitude resulted in a drop of the aftshroud temperature ( X124 ) the subsequent long HV ON period raised the temperature above "normal" readings but remained well within the limits.
FOS:
No problems were reported during the past month
On day 163 at 19:18 UTC FOS's high voltage current monitor flagged out of limits. It was determine that corrupted telemetry was the cause of the violation.
GHRS:
1.2.1 During a series of side 1 internal calibration exposures, a status buffer message was issued stating that the calulation of the Y-deflection steps needed to center the spectrum on the diode array had failed. The engineering trailer attached to the data from this exposure stated that this was a side 2 exposure. Since detector 2 was off at this time, if the Y-deflection calculation was being done on side 2, we would expect it to fail. An examination of the engineering telemetry shows activity on the side 2 integrate circuitry during this exposure, so it appears that the flight software was issuing side 2 commands. The command load has been checked and no problems were found. The flight software was idled during instrument configuration at the start of the exposure, and the flight software group is investigating this problem to determine if idling at this time could affect the side designation. If no flight software error is found, it is possible that the single bit used to designate the active side when sending commands could have taken a hit.
1.2.2 Monitoring of GHRS carrousel reset activity is continuing. During the month of June there were 2 reset events for 348 commanded positions. Figure GHRS-F4 contains a plot which shows the accumulated number of times the carrousel is commanded to a new position and compares this rate to the accumulation of carrousel resets. The trend of both of these data sets is similar. Most recently the rate of reset events has increased. This rate will be watched to determine if this represents a new trend. Figure GHRS-F4 also includes a bar chart which associates reset activity to specific locations on the carrousel. This chart shows that the rate of reset events is higher at the lower region of the carrousel step scale. The rates shown in the region of the G140M grating are mis-leading since this is a little used optical element. A single reset in this region is rated higher than it would be in a more commonly used region.
WFPCII:
No major problems were observed this month. WFPCII radiator (-V2) reached its coldest temperature yet recorded at -74.2 C (0.8 C from the red limit). The cold temperature was due to the -V2 side of the radiator rolling out of the orbital plane for about an hour and 20 minutes.
Three different sets of guide stars were acquired in "Degraded" mode.
The sky distribution of pointings in this month is shown in Fig. 2.1. Fig. 2.2 shows the monthly average pointing miss for primary guide start acquisitions and reacquisitions. The pointing miss is measured from the location of the guide star found during search compared to the predicted position (start of the search). table 2.1 describes the statistics of guide star acquisitions. It takes into account both primary acquisitions and reacquisitions. "No lock" means that coarse track cannot be established or maintained. "Degraded mode" refers to the cases where the guiding mode falls back to coarse track when the commanded mode of the find lock cannot be established or maintained. "Search rad exc" refers to cases where the guide stars are not found.
The distribution of guiding modes by Science Instrument during scheduled exposures is given in table 2.2. for each scheduled exposure, the actual guiding mode is obtained from the engineering telemetry. The scheduled exposure time is subsequently summed up by guding mode for each SI to produce the distribution.
The full-width at half-max (FWHM) of jitter during observations are plotted as a function of the magnitude of the dominant guide stars in Fig. 2.4. the jitter is obtained from the motion of the dominant guide stars in the FGS. The rms of jitter along V2 and V3 axes is also calculated for each observation. The average of FWHM and rms of jitter over all observations in each month is given in Fig. 2.3 and shows no obvious trend.
For each observation, the PMT sensitivity is calculated for each FGS in fine lock based on the PMT count rates and magnitude of the guide stars. The sensitivity is expressed in total counts of the 4 PMTs per 25 milli-seconds normalized for a 13th magnitude star with the FGS filter in pupil position. Fig. 2.5 shows the average sensitivities of each month since Janurary, 1991. The is no obvious trend. The variation of the sensitivities appears compatible to the error of the guide star magnitude.
2.2 Observations
The temperature fluctuations of critical spacecraft components are shown in Figure 3.1. All temperatures are nominal.
3.2 Costar:
The Instrument continues to operate without problems: Evaluation of Error Logs show all voltages, currents, and temperatures within their nominal limits. Serveral plots of selected monitor points critical to the performance of the Instrument are an integral part of this report: costar-p1 : Input Voltage and Current shows the Input Voltage and total current profiles. costar-p2: and costar-p3 : illustrates the Regulator Housekeeping voltages. costar-p4 : contains the RIU-A and the Main Electronic Box (MEB) temperature profiles. costar-p5: and costar-p6 : shows the FOC/GHRS Mirror arm tempertures and the thermistor reading of the Deployable Optical Bench (DOB). costar-t1 contains a table of the latest position of all COSTAR mechanisms.
3.3 WFPCII:
tables wfpc-ii t1, t2, t3 and show the June instrument statistics and profiles for cycle usage, power and temperature. All values are nominal and within limits unless otherwise noted. F4 shows the radiator cooling down to -74.2 C.
table t1 shows the cycles of various mechanisms and power supplies.
table t2 shows the lvps, mechanism, and tec voltage and current outputs.
table t3 shows the bays, optical bench, Bulkheads, Cold and Hot junctions, Camera Heads, Attach points, AFM, and Radiator temperature values.
Figure f3 shows the frequency for various shutter close/open and open/close flight times.
Figure f4 shows the cold and hot junctions, Camera Head, and Radiator temperatures.
Figure f5 shows the Bays, Optical Bench, and Cal Module temperatures.
Figure f6 shows the mechanism, tec and 22 lvps voltages and current.
Figure f7 shows the lvps, camera head, and UV Output Monitor voltages.
Figure f8 and Figure f9 shows the afm voltages and current
3.4 FOC:
FOC: The f/96 relay of the Instrument continues to operate without problems after the installation of COSTAR: Evaluation of Error Logs show all voltages, currents, and temperatures within their nominal limits.
Several plots of selected monitor points critical to the performance of the Instrument are an integral part of this report:
Four critical temperatures are shown foc-p1:foc thermal plots reflecting the thermal profile during the reporting period.
A set of three plots foc-p2:foc high voltage monitors illustrate the profile of the output voltages of the critical High Voltage Power Supplies for the FOC detectors. For a picture of the FOC Dectectors click here.
foc-p3:foc vpu noise and sds error log Both plots are focused on the health and safety of the Instrument. The Video Processing Unit (VPU) Noise level indicator summarizes the input signal as detected by the VPU. The peaks typically indicate passages throught the South Atlantic Anomaly (SAA).
foc-p4:foc mode and observation profile shows the usage of the camera over the reporting period. A reading of the Thermal Control Table Number of "2" flags the time the FOC has been in the High Voltage Mode using the f/96 relay. The value of "1" indicates a reactivation of the F/48 Camera section.
Several Tables are inserted to keep track of operational statistics in particular of limited lifetime items: Table foc-t1 illustrates the statistics of the HV cycles and the hours the FOC was operated in the High Voltage Operate Mode. The same table foc-t1 shows the MIN/MAX/AVERAGE values grouped into the different operational modes: Safemode, Hold, and the High Voltage Operate Mode.
The foc-t2: mechanism cycle/usage table summarizes the usage of the mechanism during the reporting period and adds up the total number of cycles during Ground Testing and In-Orbit use.
A statistic on FOC f/96 Observations is given in Table foc-t2: mechanism cycle/usage table This table also keeps track of the number of loss of lock that occurred during a scheduled FOC observation time and adds up the time lost on target.
For a picture of the optical path and the FOC mechanism click here.
3.5 FOS:
Table fos-t1 shows the Cycle, Voltage and Miscellaneous summaries for the FOS for the month of June. There were no health and safety of operational limit violations for the month. No additional diodes were disabled during the month.
Table fos-t2 shows the thermal summary for the month. There were no health and safety or operational limit violations for the month.
Figure fos-f1 is the standard plot of Collimator (predicted and actual) temperature (Y302) as a function of time. The predicted temperatures are based on algorithms for both the Operate (LVON) state and the Hold (LVOFF) states as a function of FOS aft shroud sink temperatures. The optical bench reacts in such a way as to be within +/- 1 deg C of equilibrium 24 hours after a transition. This plot suggests nominal thermal behavior for the detector as a whole even during the periods of continuous LVON.
Figure fos-f2 shows a nominal optical bench gradient temperature for the month. Figures fos-f3 and f4 show the Red and Blue detector dark count data for the month. These plots are a representation of the Overlite counts from the FOS at all times that the detector is in Operate mode. Overlite is an engineering telemetry monitor of the total counts on the active detector array for the last 60 seconds. The data represented here occured after HV stabilization, after dead/noisy diode disabling, outside the SAA, with the FOS aperture door shut, and all lamps off. The data are therefore total dark counts in a 60 second period for all enabled diodes. Figures fos-f5 and f6 show the comparison of June's dark count data to May's. June's dark count data represent nominal performance.
3.6 GHRS:
All trended monitors appeared normal for this reporting period. The following tables and figures summarize activity of selected areas of the instrument.
Table ghrs-t1 is a cycle and use summary of the instrument mechanisms as well as a statistical analysis of main bus voltages and currents.
Table ghrs-t2 is a statistical summary of key instrument temperatures. All temperatures are within their normal range.
Figure ghrs-f1 contains plots of key instrumental temperatures. The temperature profiles for each detector and the optical bench are shown since these temperatures can affect optical stability. The temperature plot for MEB 1 is also included since large operational gradients on this monitor contributed to the intermittant failure on the side 1 low voltage power supply.
Figure ghrs-f2 shows the side 1 and side 2 power supply voltages for the month. These voltages remain very stable.
Figure ghrs-f3 contains monthly power profiles for each side of the instrument as well as historical summaries of hours spent in OPERATE mode.
