Monthly Observatory Report
for
November 1994
COSTAR:
There was no COSTAR activity during this reporting period. The instrument remained in HOLD mode and was stable.
WFPCII:
WFPCII continues to operate nominally throughout the month of November.
The transition from a 12 hours monthly decontamination to a 6 hours decontamination took place on day 323. The change was brought about since there was no significant difference in the hot pixel rates between the two decontamination periods. UV throughput was restored to nominal value.
Science and Calibration observations continue to execute successfully.
The WFPCII TEC radiator temperature study has been completed. The thermal radiation analyzer system (TRASYS) was used to calculate the orbital fluxes, and radiator thermal coupling with HST and the environment. The system improved numerical differencing analyzer (SINDA) was then used to calculate the modeled TEC radiator temperature profiles. The results show that the lowest temperature at which the radiator will cool down to is -72 C for Sun angle=90 degrees and Beta angle=+/- 52 degrees. The variation of the Roll angle according to the model has little effect on the minimum radiator temperature. When the hot junction power was reduced by 7 watts, the radiator temperature cooled to -74 C. Removing all hot junction power (TECs Off) caused the radiator temperature to drop to -77 C. The result of the thermal math model correlate well with flight data. However there is still an uncertainty of +/- a few degrees. The lowest radiator temperature recorded in orbit is -72 C. The next calibration point is -74.4 C which is still above the -75 C TEC Off limit.
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.
FOS:
The FOS continued to execute a variety of GO, GTO, and CAL proposals during the month of November.
GHRS:
Both side 1 and side 2 of the GHRS are running without problems.
1.2 Summary of major problems
COSTAR:
None.
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 after the Servicing Mission. HSTAR 5000 "FOC TCE Control Table Number mismatch" has been filed. The Configuration Monitor program was executed DURING the transition of the Instrument from Hold to Warm-up mode. The extraction of the TCE control table number show nominal values. The closure notice has been submitted.
FOS:
The FOS Blue detector was recovered after the instrument safing last October. All high voltage operations with this detector have been nominal since the recovery. The event that triggered the safing has been categorized as an anomalous micro processor reset.
GHRS:
1.2.1 Monitoring of GHRS carrousel reset activity is continuing. During the month of November there were seven reset events for 418 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. 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. 1.2.2 Implementation and test of the GHRS flight software fix that will allow observation time-outs is underway. The flight readiness review for this fix is tentatively scheduled for January 13, 1995. 1.2.3 An error was found in the management of GHRS soft-safing. When soft-safing was developed for the GHRS, only side 2 of the instrument was used. Soft-safing was not modified when use of side 1 was resumed, which could have resulted in continued side 1 operations during a spacecraft safing event. The safing table has been revised to take into account side 1 operations.
WFPCII:
Investigation of WFPCII data dropout due to shifted sync bits (HSTARs 4930, 4954, and 4956) shows that the shift may be traced to the period of the science data readout. A plot of the CU/SDF time tag for each packet readout shows that some abnormal time delay occurred during the CCD readout from the WFPCII to the CU/SDF. This may have caused the data segment sync pattern to be displaced. It is not clear what caused the delay. Further investigation will be done. A 1800 seconds calibration dark taken on day 294 shows a median level of about 4 to 5 DN higher than other normal darks. All engineering telemetry were checked for possible light leak through the shutters. The shutter logic and speed flags for the preceding exposure were normal. The telemetry command echo were verified to be correct. Some correlation work was done in regard to the HST bright earth viewing during the exposure. However some darks have shown higher bright earth fluxes during the exposure period but show no abnormal (high) dark levels. Comparison of the intensity of the PC to shadow and WFC to shadow were done and the results correlate to the respective camera f ratio. This may indicate that some form of light came through the optical path. There has been some discussion whether residual effect from the UV lamp is causing this effect. Further work will be done. On day 324 at 02:31:33 WFPCII flagged the second microprocessor timing error. The anomaly is currently being investigated.
Four different pairs of guide stars were involved in the 12 cases of 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 costar trending program is being developed. Table costar-t1 has been included to document current mechanism positions associated with the COSTAR mirrors.
3.3 WFPCII:
tables wfpc-ii t1, t2, t3 and Figures WFPC-II F3-F9 show the November instrument statistics and profiles for cycle usage, power and temperature. All values are nominal and within limits unless otherwise noted.
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 November. 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 November's dark count data to Octobers's. November'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.
