From tsuneta@flare1.solar.isas.ac.jp Fri Oct 25 06:58:44 1991 Received: by isass0.solar.isas.ac.jp (5.57/Ultrix3.0-C) id AA22004; Fri, 25 Oct 91 06:58:03 +0900 Received: by flare1.solar.isas.ac.jp (5.65/ISAS-SOLAR1.0/A) id AA04555; Fri, 25 Oct 91 06:57:33 +0900 Date: Fri, 25 Oct 91 06:57:33 +0900 From: Saku Tsuneta(IAUT) Message-Id: <9110242157.AA04555@flare1.solar.isas.ac.jp> To: hara@flare1.solar.isas.ac.jp, morrison@isass0.solar.isas.ac.jp, ogawara@nasamail.solar.isas.ac.jp, shimizu@flare1.solar.isas.ac.jp Status: RO SXT operation manaul #1 Rev. A: October 24, 1991 S. Tsuneta This memo summarizes some important issues of SXT operation during KSC contacts. The guideline for SXT operation is as follows: 1. to operate SXT with minimum number of useless images, (images not recorded in BDR, imcomplete images, and night-time images) 2. to operate SXT at KSC with minimum disturbance to the SXT observing sequence, 3. to find possible SXT anomaly as early as possible at KSC contacts. Keep always in mind that you are responsible for operation, health, and science output of one of the most precious telescopes in this century. 1. Two important commands Understanding of the following two commands is essential for SXT operation. a. DC (Discrete Command) SXT CONTROL AUTO/MANUAL AUTO mode: SXT observation mode No command except SXT CONTROL MANUAL is acceptable. MANU mode: SXT standby mode Manual mechanism move (eg for weekend photon-flood operation) and table upload are done in the standby mode. Note: There is a case that SXT CONTROL mode is automatically changed to MANUAL. This is done by the flight software to protect SXT from malfuction, when the error flag is set. b. DC SXT (BDR) CHECK ENA/DIS ENA mode: SXT observation and the associated telemetry data transfer are done only when BDR is in RECORDING mode. If the BDR is in PLAYBACK or STANDBY or OFF mode, SXT observation will be halted. DIS mode: SXT observation and the associated telemetry data transfer are done regardless of the state of BDR. SXT CHECK ENA/DIS state was prepared to prevent the SXT observation when BDR is not in the recording mode for minimizing the mechanism motion and X-ray radiation to CCD. 2. How to use SXT CHECK ENA/DIS for KSC contact KSC LOS-OG contains DC SXT CHECK ENA, so that the SXT CHECK mode is always ENA for the non-contact time. The procedure for SXT CHECK command differs, depending on the DAY/NIGHT of the spacecraft. Case A. Spacecraft is in the DAY phase during the whole contact. |<----------------->| |<----------------->| ______*________D___________________E_+_D____*_____*________E______________ ^ ^ by LOS-OG BDR PLAYBACK Telemetry drop-out (DC) phase for antenna ^ change etc BDR RECORDING (DC) ^ BDR goes to STANDBY automatically. E=DC SXT CHECK ENA D=DC SXT CHECK DIS |<---->| period when image data is available. BDR STANDBY mode follows the BDR PLAYBACK automatically. By commanding SXT CHECK DIS, the SXT observation resumes, and the real time image data becomes available. Note that SXT CHECK ENA msut be sent before the antenna change or the known telemetry drop-out (due to the antenna angle constraint) to halt SXT for possible telemetry drop-out. After confirming the telemetry recovery, the image data is is again available by sending SXT CHECK DIS. Always send SXT CHECK DIS when there is a possibility to loose the precious image data. If KSC alerts you to the bad quality of the telemetry line, stay on SXT CHECK ENA. (DC MODE CONTROL AUTO is contained in the LOS-OG, the DP mode remains the manual QT-H or FL-H set during the contact even in the spacecraft night until the LOS-OG.) Note: The last SXT CHECK ENA will be included in the LOS-OG, which may be done after the actual loss of contact at KSC. If the night comes in between the actual loss of contact and LOS-OG, DC ACS-H has to be manually sent before the loss of the contact. (Since DC MODE CONTROL AUTO is contained in LOS-OG, the DP mode remains in the manual QT-H or FL-H set during the contact even in the spacecraft night until LOS-OG.) CASE B Spacecraft is in the NIGHT phase during the whole contact. Since we should not take images during night (unless there is specific purpose), we stay in SXT CHECK ENA mode. But, this is not a sufficient condition for not taking images at night: when BDR PLAYBACK is completed, and the RECORDING MODE starts, SXT observation also starts, because DP mode is manually QUIET HIGH or FLARE HIGH above KSC even when the spacecraft is in the night phase. ______*_________________*_____________*__________*_________________________ ^ ^ BDR PLAYBACK BDR STANDBY DP ACS-H BDR REC (DC) (automatic) (DC) (DC) By sending DC ACS HIGH command prior to DC BDR RECORDING, we can completely avoid SXT imaging at night, because there is no telemetry allocation for SXT in ACS format. The DP mode at the start of the contact is also ACS-H mode with the DC ACS HIGH contained in AOS-OG for SXT purpose. DP mode change to QT-H or FL-H mode is done after BDR PLAYBACK start. CASE C There is a transition from DAY to NIGHT during contact. You can take images by sending DC SXT CHECK DIS in the DAY phase. However, instruct SSOC duty personnel that DC SXT CHECK ENA has to be sent prior to the start of the spacecraft night. Also, DC ACS HIGH command has to be sent prior to DC BDR RECORDING command. If you do not require realtime image data, you can follow the case B procedure. S/C DAY phase | NIGHT phase(Not DP mode) ________*______________________*____|________________*____*_____________ ^ ^ | ^ ^ DC SXT CHECK ENA DC SXT CHECK DIS ACS-H BDR REC Case D There is a transition from NIGHT to DAY during contact. SXT CHECK DIS command, if you require the realtime data, has to be sent after the spacecraft enters the day phase. 3. DSN contact No special SXT activity is required for DSN operation. Since SXT CHECK mode is ENA, the SXT observation and the image data telemetry are both halted during DSN playback. The image taking and the image data telemetry will be resumed, as soon as BDR starts the recording. (This arrangement is necessary, because the realtime telemetry channel is not available for DSN station passes.) 4. How to quick-check the health of SXT It is duty operator's responsibility to carefully check the SXT status (following the check sheet) and to examine the real time or the playback image data. There is no clear-cut way of knowing the SXT health. But, check the following points: a. SXT error flag SXT error flags are RED-displayed on any page of the quick look. If you find the error, please go to the page 4 of the quick look to get more information on the error. Note: The false error flag may be set due to the telemetry drop-out. Confirm that the error flag is real by resetting the quick look error flag with PF24. (The error flag display on the quick look is of latching type. Thus, even if there is transient false-error flag only in one major frame, it will remain on the display.) Spacecraft quick look also shows the error status in the SXT section of the display. b. Watch SXT exposure realtime status on quick-look page 2 During KSC contact, watch SXT exposure and mechanism status shown on the page 2 of the quick look. Note that the default shutter position is CLOSE during the normal observation, while the shutter is OPEN with the fliter wheel configration B=1/A=3 at night time, and during the MORNING phase (4 minutes) following the night. c. Image data Confirm that the proper images are taken in both FFI and PFI. Also confirm that the observing region location is OK. d. Image serial number Check the continuity of the image serial number. If there is a significat gap (larger than 50), check why the gap happened. (Since BDR image data is over written, some data loss is inevitable.) e. Mechanism serial number Briefly check the odometers of the filter wheel, the shutter and the aspect door. Confirm that there is not significant change in the number. (Recently, there is no aspect door commnading, so that it should stay If you find the anomaly during the contact, stop SXT following the emergency procedure, and try to reach the following personnel: S. Tsuneta home 0423-35-0386/office 0422-41-3640(Inst. of Astronomy) T. Shimizu 0424-80-4173 H. Hara 0424-80-5208 end of message