MTA Monitoring Report 4/20/01 - 04/26/01

Archive of all weekly reports

Archive of Monthly reports

At approximately 10:20pm on Friday Chandra was found to be in normal sun mode unexpectedly. A detail description of the event described in Jeff Shirer (jshirer@cfa.harvard.edu) email (Thu, 26 Apr 2001 13:56:16 -0400) is attached at the end.

Radiation

Quiet during this period.

ACIS/Radiation Environment correlations

CTI Trend

Average of ACIS-I CCDs (MnKa) slope 1.780e-8 CTI/day
Detrended slope 1.448e-8 CTI/day

ACIS Warm Pixels

The following front-illuminated pixels consistently showed a bias level more than 5 sigma away the chip's mean level during this period (Note:a definition of a warm pixel was changed to match with that of MIT).
For more information on these and the back-illuminated chips, see the link above and MTA monthly reports.

ACIS Focal Temperature

For this period, 2 peaks are observed.

MTA Problem Tracking

Several PCAD related flags were raised. There are related to the bright star hold and normal sun mode entries.

04/21/01
AOBRTSUC (BRIGHT STAR ACQUISITION SUCCESS FLAG)
AOIRURT4 (IRU CHANNEL 4 RATE FLAG)
AOIRURT3 (IRU CHANNEL 3 RATE FLAG)
AOIRURT2 (IRU CHANNEL 2 RATE FLAG)
AOIRURT1 (IRU CHANNEL 1 RATE FLAG)
AOPSACGN (ATT_CMD_GEN S/W STATE)
AOPSATUP (ATT_UPDATE S/W STATE)
AOPSFFTQ (FF_TORQUE S/W STATE)
AOPSPTCL (POINT_CON_LAW S/W STATE)
AOPSCATM (CMD_ATT_MON S/W STATE)
AOFSTAR (KALMAN FILTER STAR CATALOG SOURCE)

04/22/01
AIRU1R2Y (IRU-1 RANGE 2Y)
AIRU1R2X (IRU-1 RANGE 2X)
AIRU1R1Y (IRU-1 RANGE 1Y)
AIRU1R1X (IRU-1 RANGE 1X)

Following msid violation continues to recur
ESAPYI

SIM Movements

7 TSC moves this period
weekly average time/step 0.00133 s
mission average time/step 0.00139 s

Telemetry

Everything is quiet and in an expected range.


Recent Observations

The ACA Problem is in the specified handling of guide star positional errors.
This issue in not significant to the final product and so is being worked at low priority.
OBSID DETECTOR GRATING TARGET ANALYSIS ACA
1044 ACIS-S NONE SN1987A OK PROBLEM
1029 ACIS-S NONE SMCX-1 OK OK
1660 ACIS-I NONE V1121+2327 OK OK
2453 ACIS-S NONE 3C228 OK PROBLEM
2072 ACIS-S NONE NGC4552 OK OK
2458 ACIS-S NONE SGR1900+14 OK OK
1901 ACIS-S HETG V603AQUILAE OK /OK OK
711 ACIS-S NONE AQLX-1 OK PROBLEM

Trending

This Week's focus HRMA THERMAL GRADIENTS
Temperatures in degrees K.
Current in Amps.
Voltage in Volts.

Most msids are keeping the same trends from the previous reporting period ( 02/02/01 - 02/08/01 weekly).
Interesting trends are indicated with "*".

Normal Sun Mode entry

Email from Jeff Shirer (jshirer@cfa.harvard.edu) Thu, 26 Apr 2001 13:56:16 -0400

Events leading up to the NSM entry (D. Shropshire):

A TOO request was received on day 108 with a 1 to 3 day turn around. FOT MP, with the help of SOT MP, developed a plan to insert the TOO observation into the currently running ARP1701B loads by intercepting after the radiation belt passage on day 111:02:00. The loads were built on day 109 and approved on day 110. The Intercept method, chosen to insert the TOO, required that the APR1701B loads be halted and the new APR2101B TOO loads uplinked in their place. This was done on day 110:18:00:00 by CAP 719. At approximately 111:00:30, Chandra entered Normal Sun Mode due to the loss of stars in the ACA as the Earth passed in front of the camera field of view.

The Earth occultation was not anticipated or planned, but was rather the result of an Earth avoidance maneuver being dropped from the APR2101B TOO loads by FOT MP. The original Earth avoidance maneuver, as scheduled in the APR1701B loads, was to take place at 110:23:08. Since the APR1701B loads were halted at 110:18:00, this maneuver was never executed, and since the APR2101B loads started at 111:02:00, this maneuver was not included. Therefore, the last attitude in the APR1701B loads, which was Earth occulted, was held until the time when the Earth drifted into the ACA field of view.

NSM Transition Timeline:

2001:111:00:26:50 - Start losing guide stars
2001:111:00:27:54 - Guide star success flag goes to "NSUC"
2001:111:00:27:53 - Start of 6 tries to find acquisition stars
2001:111:00:31:15 - Start of 4 tries to find bright stars
2001:111:00:31:16 - Bright Star/ Cmd Attitude Mon. Trip
2001:111:00:35:11 - Sim reaches midpoint
2001:111:00:35:33 - Bright star success flag goes to "NSUC"
2001:111:00:35:34 - Attitude reference monitor trip (AOPCADMD = NPNT
and AOBRTSUC != SUC)
2001:111:00:40:08 - Sim reaches HRC-S
2001:111:02:20 - AOS, OC discovers safing action

Recovery Steps (R. Cameron)

111/2150: start CAP 720.
111/2209: transition to NSM during SOP 56005, in CAP 720.
111/2347: start CAP 720 rev C.
112/0000: start SOP 56005
112/0006: acquire bright stars
112/0110: perform attitude update
112/0140: complete maneuver to starting attitude for APR2201 load
112/0150: end of SOP 56005, CAP 720 rev C.

114/2045: start CAP 721
114/2055: enable RW bias
114/2105: end CAP 721