At 13:55 UT this morning the operations by the FOT went smoothly and submode 6 telemetry was resumed. The LEB was working properly and EIT was allowed to send a single command to get images for pointing corrections at 14:46 UT. Click here for the first image showing the pointing. We are currently rolled -120 degrees so the North Pole appears to be the South West. Sun center is approx. 1 arc minute off which will be adjusted today.
SOHO will remain in this roll position until March 1st scheduled correction date.
Be sure to check the LASCO daily status page for times and events.
Scheduled transition to medium rate telemetry is currently set for Tuesday Feb 2nd and NRT may be possible late that day.
Check the SDAC Home Page for a look at a well deserved FOT "Thanks".
The LASCO and EIT cameras will be going through full calibration sequences after the initial instrument status has been determined. EIT will be delaying the planned CCD bakeout for the time being.
The time-line for instrument medium rate telemetry is Tuesday February 2nd. Normal observations and cadence will resume after the calibrations are complete.
Station Keeping maneuver #3 while in ESR mode executed today. Correction of delta-V of 3.8 m/s with fuel usage of 4 kg.
NASA/ESA engineers have developed a new program for the delta-V correction which will not oppose the ESR thruster firings and will conserve the S/C fuel usage for the maneuver.
Flight Operations Team had a very busy weekend.
Tests were run and successfully completed to reduce the ESR thruster firings from 15 per 1 hour time-span to 6 per hour. While the ESR gives numerous thruster pulses automatically, the objective is from the ground to give a minimal opposing thruster pulse to 'slow' the return of the S/C before the ESR would send its large opposing pulse. This test cut fuel usage by one-half and is currently implemented.
To transition back to RMW mode, one option is to lock the guide star tracker. Two tests were done over the weeekend and successfully gained lock and tracked for several minutes during a low roll activity period. Once RMW mode is obtained, reaction wheels and star tracker mode will be used for control which will eliminate the thrusters and fuel consumption. Software changes will be made to eliminate the need for gyros.
Plots of the OCC 1,2,3 , the Z micrometer and the changes of the PZTs below:
Plots of the OCC 1,2,3 and Z micrometer below:
Plots for the OCC 1,2,3 and Z micrometer voltages below.
FP plots below show the OCC 1,2,3 and Z micrometer voltages for this period:
Plots of the OCC 1,2,3 and the Z micrometer voltages below.
We saw many changes in the Z micrometer and OCC (Optical Control Channel), 1, 2, and 3 voltages. Plots are made for the time periods of interest:
This is a saturation of the Z micometer in the 'extreme' opposite 'long-side' of the cavity. The cavity length and the range values will be determined along with the 'null-point' in the Z Offset to set the Range DAC as close to zero as possible. This will give a 'readable' range factor.
Continued analysis and FeXIV/Clear images are being taken at a 2 hour cadence while still the LASCO COB heater zones being increased by +5.5 degrees.
The three PZTs are operating at full 112 volts while the DACS were dropped to zero. In hopes to align a range between the mirror plates in high and DACS in low, we will see with the known change in electronics and the error to the full cavity length of 43mm, + or - 6mm.
The LASCO heater zones were increased + 5.5 degrees to again 'flex' the LASCO COB and restart the 'walk-off' correction. FeXIV/Clear images at a 63 second exposure with a 2 hour cadence continue for analysis.
C1 FP testing showed a ceiling to the mirror plate correction recovery. We will attempt to manually adjust the plates to parallel. A manual adjustment will be determined by aligning the plates and taking the images. PZT #3 was adjusted to zero volts while PZTs 2 and 3 remain at 100 volts. We will take images in FeXIV/Clear at 63 second exposures on a 2 hour cadence for analysis.
C1 is continuing the FeXIV/Clear door closed program with a 1 hour cadence. We have found using the 3 hour cadence for the days of Nov 9th-12th, the PZTs are "on their own" recovering. The images are showing a linear correction to the mirror plate 'walk-off' with a +25% improvement from the images of reference dating Oct 22nd. We are increasing the cadence and will study further the changes that are taking place in the FP.
The images are going to be used in animation sequence to determine if the mirror plates are seeing change in succession as the PZTs are kept at constant voltages while in servo mode.
|
COB Zone |
Nominal
|
Nominal
|
Adjusted
|
Adjusted
|
| LASCO 1 | 110 | 15.5 | 97 | 19.7 |
| LASCO 2 | 106* | 16.8 | 96 | 20.0 |
| LASCO 3 | 109* | 15.8 | 95 | 20.5 |
| LASCO 4 | 110 | 15.5 | 94 | 20.8 |
| LASCO 5 | 110 | 15.5 | 94 | 20.8 |
The thermal cycling was an attempt to correct the current wedge defect of the misalligned mirror plates by intentionally causing flex in the box, then making the necessary adjustments in the PZTs before the cool-down begins. Reference images were taken before and after in FeXIV/Clear filters to verify settings.
Continued evaluation and preparations being made for the next test to begin Wednesday November 4, 1998.
The C2 polarized brightness images are perfect and will be of needed use in the upcoming 40 hour SPARTAN-201-5 mission for calibration scheduled for November 1st.
C3 is found to have pressure on the zero degree polarizing filter. This is dissapointing, but having the +60 degree and -60 degree filters correct, we can get the appropriate values for the defective zero degree filter and still get accurate sums in the images.
C1 FP testing and commissioning to resume Thursday Oct 29th.
These images are quite similar to the previous evenings images.
Oct 22 20:44:53 UT Notice the extension of the walk-off. This is showing the wedge defect to a different plane than noticed earlier.
This M-Peg of Oct 22nd shows the 5 images together. This helps to notice the change.
We have seen the movement now from all three PZTs. We have also determined the cavity length is outside of the electronic range of the cap mics, which also the wedge defect is outside the range of the PZTs to compensate for it.
The next step will be to determine the actual cavity length.
As you notice in the image of Oct 21 23:14:06 UT the wedge polar coordinates angle is about 120 deg.
The image of Oct 21 23:23:11 UT shows the wedge polar coordinates angle is slightly increased after a voltage step increase.
The image of Oct 21 23:54:44 UT shows a drastic polar coordinate change to 60 degrees after voltage increase.
The image of Oct 22 00:17:30 UT takes the walk-off back to the polar coordinate angle of 120 degrees.
Then after going to full +112V the image of Oct 22 00:31:07 UT saw the return of the image from Oct 20th. This was an expected movement of the PZT's and from here we happily called it a night.
The checkout of the FP started by sending commands to set the PZT voltages to specific values while in reduced capability mode. In this mode, no change in the capacitance microcrometers were detected, while the error signal increased. Checkout will continue.
An analysis of the C3 door calibration images reveals a 1-2% change in the C3 polarizer transmittances in the small region where the calibration window appears. The inability to do the C3 polarization calculation can not be explained as a simple change in the polarizer transmittance. An analysis of the calibration lamp images shows a considerable change in the 0 degree polarizer from before the extreme cold soak.
After the initial images, polarization sequences in C3 and C2 were taken, followed by a synoptic sequence in EIT. Evaluation of the pB images shows no problems with the C2 images, but does show a problem when we calculate pB for C3. We will be performing a detailed calibration of the filter transmittances this weekend after which we may understand the problem in calculating the C3 pB.
Evaluation of the noise and bias levels in EIT and C3 images, shows no change in those parameters.
The C2 and C3 doors were closed in preparation for the spacecraft maneuvers tomorrow.
The continued operation in EIT, C3, and C2 is giving us more confidence in the stability of the instrument. In summary, the LEB, EIT, C3 and C2 are all functional. The only mechanisms that have not been checked on the three telescopes are the EIT door, the C2 focus and the C2 IOCS. Absolutely no errors have been detected in the operation. Detailed calibration activities will be proceeding during the next days to weeks. The functional checkout of the C1/FP system will hopefully take place next week.
Checkouts of the LEB and EIT have been completed and they work perfectly! All five processors in the LEB and EIT along with the four in the COB are working perfectly, with no hiccups at all in the inter-processor (or intra) communications, etc. ICE and OBE booted up out of EEPROM, showing that it survived and giving us the revised versions of those two modules (the others were the same as in bipolar ROM). The thermal control of the COB and EIT has been switched to internal (LEB) control and is holding the temperature zones to the proper values. With this new thermal environment, the internal temperatures will probably shift over the next few hours.
EIT images in all four sectors have been taken and are absolutely beautiful, showing the benefit of having been "baked out" at a higher temperature than we can achieve normally. This is the result of the amazing achievement by the SOHO recovery team. THANK YOU. EIT camera functions (ie, read out port, on-chip summing, sub field readout, heaters) were verified. The sector wheel worked normally. The checkout of the EIT filter wheel was deferred until tomorrow.
Dark images (0, 60, 300 seconds) from all telescopes have been acquired. As expected, some shifts in the bias values are noted, but more analysis will need to be made. Qualitatively, all the CCDs appear to be in good shape, with no extra hot or dark pixels detected. The temperatures of the CCDs were about 3 degrees warmer than they had been, but still very cold. This might be due to the camera temperatures being slightly warmer than they will be when they get to the normal operating condition.
All shutters and calibration lamps in the EIT and COB are working properly. The C2 filter and polarizer wheels are also OK. The FP status is consistent with the concept that the piezoelectric crystals are not working, but we have not done the testing to prove it.
The pointing of the COB as determined by the boresighters is about where it was in June. The BS-Y boresighter continues to show a slight drift. EIT shows that the pointing is also where it was. The roll of about 50 degrees will be corrected at the next station keeping manuever, currently this friday.
Most of the testing was done today in telemetry submode 1 (5.2 kbps) but then it was switched to submode 5 (7.9kbps). No problems at all in either submode. Submode 6 will be uploaded soon, giving us nearly 15.8 kbps.
Testing will continue on the COB tomorrow after a full set of EIT images is taken.
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