Recover from SAFE or Spacecraft safehold

Version 15 - Last modified 22 Dec 2011

Location

Written procedure on Docushare: https://www.swift.psu.edu/docushare/dsweb/View/Collection-127
Further detail: http://www.mssl.ucl.ac.uk/swift/docs/procedures/

Background

When the S/C enters Safehold mode the UVOT will be placed, via a S/C RTS, into one of three states:

A. Recover from SAFE state

Purpose

Return to IDLE state to continue observing after being in SAFE state.

Steps to run

If the safety circuit has tripped, see the procedure for recovery from safety circuit trip instead.
  1. Make sure you understand the cause of the UVOT ICU going to SAFE state
  2. start icu_idle
If this fails with the error "Exit From Safe Forbidden" then run and try again

B. Power on UVOT DEM and redundant telescope with PRIME focus heater after complete UVOT power off or both TM power off

Purpose

Power on the PRIME DEM PRIME and turn on prime secondary mirror focus heater then power off and power on REDUNDANT DEM and TM.

Steps to run

Skip 1, 2 and 3 and instead start at 4 if UVOT is completely powered off (Both DEMs and both TMs)
  1. start icu_tdrsshk_on(100) [0min]
  2. start dpu_tdrsshk_on [0min]
  3. start uvot_power_off [3min MAL or 10min TDRSS]
  4. start uvot_power_on("PRIME", "AB") [5-7min MAL (or 12min TDRSS)]
  5. start idrift [7s MAL]
  6. start iearth_constraint [20s MAL]
  7. start imoon_constraint(19) [20s MAL]
  8. start ifocus(sec, 1000) [30s MAL, 3min TDRSS]
  9. start icu_tdrsshk_on(1000) [0min]
  10. start icueeprom(0x391) (0x3c3 for TDRSS) [5min MAL or 10min TDRSS]
  11. start uvot_coldfocus [1min MAL, 5min TDRSS]
  12. start uvot_power_on("REDUNDANT", "AB")    --see note at end of doc [7min MAL (or 9min TDRSS)]
  13. start sc_poweron_pri_uvot_tm_a [7s]
  14. start icu_tdrsshk_on(1000) [0min]
  15. start icueeprom(0x391) (0x3c3 for TDRSS) [5min MAL or 10min TDRSS]
  16. start isubthrespt(0x01AA)
  17. start icu_idle [5min]
  18. start icu_tdrsshk_on(480) [0min]
  19. re-enable alerts (SERS and GCN), if disabled
  20. edit, CVS and deliver uvot_limits.proc - change limits of SBCTXERRCNTICU, SBCTXERRCNTDPU and D_BOOT_CNT.

C. Power on UVOT redundant telescope module after redundant TM power off

Purpose

Power on redundant TM. Return to observing.

Steps to run

The first proc checks the filter wheel position, heater control, resets safety circuit if necessary, and initializes the TM (approx. 3 min). The second proc starts a UVOT RTS which slowly transitions to Idle state by ramping up the high volages ready for observing triggered by the next slew.
  1. start uvot_tm_recovery(redundant, ab)
  2. start icu_idle

D. Cycle power of DEM

Purpose

Power off and then power on the redundant DEM for example if the DPU is stuck.

Steps to run

You might want to stop the heartbeat limit violation with something like this: /ICHANGELIMITS ITEM=0x2a, LOW=0, HIGH=0
  1. start icu_tdrsshk_on(300) [TDRSS]
  2. start dpu_tdrsshk_on [TDRSS]
  3. start uvot_power_off     but see below ... [3min MAL or 10min TDRSS]
  4. start uvot_power_on("REDUNDANT", "AB")    --see note at end of doc [7min MAL (or 12min TDRSS)]
  5. start sc_poweron_pri_uvot_tm_a
  6. start isubthrespt(0x01AA)
  7. start icu_idle
  8. edit, CVS and deliver uvot_limits.proc - change limits of SBCTXERRCNTICU, SBCTXERRCNTDPU and D_BOOT_CNT (and SBCRJCTTC_DPU if necessary).

    *** Note on dpu_bootconfim patch loading ***

    If dpu_bootconfirm fails (waits forever on the confirmation line of the proc), run 
    start /istate idle
    wait 30 s
    and try 
    start dpu_boot_confirm
    again.

    Repeat dpu_bootconfirm if it fails again.