MTA Monitoring Report 11/24/06 - 11/30/06

Archive of monthly reports

Radiation

Quiet.

Detrended CTI

Although we have quoted CTI values of the cleanest data (FT <= -119.7 C, int time > 7000sec), the data fills these conditions are getting rare. From this week, we quote CTI temperature factor corrected ones. The values in the parentheses are CTI based on the cleanest data.

Average of ACIS-I CCDs (MnKa) slope:	2.430e-9 CTI/day	(3.193e-9 CTI/day)
Detrended slope:	7.000e-9 CTI/day	(7.456e-9 CTI/day)

ACIS Warm Pixels

	CCD0	CCD1	CCD2	CCD3	CCD4	CCD5	CCD6	CCD7	CCD8	CCD9
Previously Unknown Bad Pixels
Current Warm Pixels		(802,665)	(526,66)	(703,739) (811,637) (931,553)	(227,467) (247,364)	(109,1) (233,321) (233,322) (233,323) (233,324) (233,326) (233,327) (233,325) (258,797) (263,317) (280,313) (352,544) (367,511) (369,376) (669,577) (1023,166)	(360,249)	(335,412)	(356,902) (829,997)	(569,1016) (636,819)
Flickering Warm Pixels		(802,665) (910,239)	(526,66) (685,439) (764,98)	(703,739) (7721,765) (811,637) (843,781) (931,553)	(227,467) (247,364)	(109,1)(233,315) (233,321)(233,322) (233,323)(233,324) (233,325)(233,326) (233,327)(258,797) (263,317)(280,313) (352,544)(367,511) (369,376)(669,577) (745,313)(792,313) (1023,166)	(360,249)	(335,412)(662,995)	(157,47) (197,241) (356,902) (587,544) (829,997) (1024,456)	(569,1016) (636,819) (760,234)
Current Hot Pixels
Flickering Hot Pixels
Warm column candidates	509 518		509							509
Flickering Warm Column Candidates	514 518 1021		1021				509		509 514 1021	509

ACIS Focal Plane Temperature

For this period, 5 peaks are observed.



Day (DOY)	Temp (C)	Width (Days)
328.42	-118.09	0.63
329.11	-115.83	0.41
330.91	-117.61	1.77
331.31	-118.25	0.36
333.71	-117.61	1.46	the next peak start at 334.01


Weekly focal plane temperature with sun angle, earth angle, and altitude overplotted. Sun angle is the solar array angle, that is the angle between the sun and the optical axis (+X axis). The earth angle is the angle between earth and the ACIS radiator (+Z axis). Altitude varies from 34 kkm to 128 kkm.

SIM Movements

Telemetry

IRUs

• Gyro Bias Drift
• Gyro Bias Drift Histogram

Recent Observations

Trending

This week's focus is EPHIN.

Trends last reported on Sep 07.

Only the most interesting or representative msids are shown below. For a full listing choose the bulletted link.

• EPHIN Temperatures and Electronics

MSID	MEAN	RMS	DELTA/YR	DELTA/YR/YR	UNITS	DESCRIPTION
5EIOT	330.27	13.70	2.754e+00	-1.670e+00	K	EIO TEMP
5EPHINT	303.35	6.56	3.208e+00	1.832e-01	K	EPHIN TEMP
HKBBIASLEAKI	0.64	0.32	6.308e-02	-1.172e-01	uA	EPHIN HOUSEKEEPING B-BIAS: LEAKAGE CURRENT (5EHSE500)
HKCBIASLEAKI	33.25	11.43	8.195e+00	3.094e+00	uA	EPHIN HOUSEKEEPING C-BIAS: LEAKAGE CURRENT (5EHSE600)
HKDBIASLEAKI	30.10	10.51	5.551e+00	2.635e+00	uA	EPHIN HOUSEKEEPING D-BIAS: LEAKAGE CURRENT (5EHSE700)
HKEBIASLEAKI	33.01	10.80	4.499e+00	2.450e+00	uA	EPHIN HOUSEKEEPING E-BIAS: LEAKAGE CURRENT (5EHSE800)
HKP27I	6.36	1.01	4.789e-01	2.920e-01	AMP	HK 27 Volts Rail - Current
HKP27V	25.57	3.84	-8.058e-01	-1.062e+00	V	HK 27 Volts Rail - Voltage
TEIO	305.63	16.81	2.018e+00	4.315e+00	K	EPHIN ELECTRONICS HOUSING TEMP
TEPHIN	303.54	6.89	3.158e+00	6.814e-01	K	EPHIN SENSOR HOUSING TEMP

SJW: From the trending report the OBA heating does seem to be accelerating though it is still less than 0.5K/yr. The upper envelope seems to be warming at twice this rate.

Mark Freeman:This is a result of degradation of the teflon of the silver-teflon outer layer of the OBA blankets. As the material turns brown and opaque (and crazes, usually), the second-surface silver no longer controls the solar absorptance and the outer layer of the MLI blanket becomes hot. The radiative insulation of the inner layers is still present and attenuates the connection to the hot surface, but as more and more of the surface becomes warmer than the OBA control temperature, the trend will continue. Since the darkening is related primarily to solar exposure, the degradation is most rapid on the top-most section of the OBA, and decreasing with the cosine of the angle as you go around the tube. My guess is that the "backbone" MLI is pretty dark now (we know that the EPHIN housing is very dark at this point), and as you move around it is less so but darkening as well. Presumably the MLI on the dark side of the OBA isn't darkened at all, but it doesn't really matter since the emittance of the outer layer doesn't change much regardless. The good news is that this process does end (sun side MLI all brown). The question is whether or not this particular condition is OK operationally or not. My guess is that it is; I guess we'll all find out...or not that end is a tolerable

FSS Bracket
Paul Viens: In response to the questions that were noted in this MTA report, I checked with Eric and Tan, and we would like to provide the following feedback:
The EPHIN temperatures are high, but this is not unanticipated (though the predictive model coefficients do need to be updated soon, and this is in work).
As for the Fine Sun Sensor ... yes, TFSSBKT1 & TFSSBKT2 experienced mission highs of 172.2 degF last week. This is part of the heating trend of the -Z side of the spacecraft. Dan Shropshire, Eric Martin, and Tan Trinh visited Adcole (the sensor manufacturer) a couple years ago, and confirmed a similar sensor had been qual tested to 90 degC = 194 degF at the sensor head. Our telemetered bracket temperatures (TFSSBKT1 & TFSSBKT2) are 8 degF colder than the head, so we have set our red limit at 186 degF. While this limit update was made in GRETA following an FDB presentation in Feb 2005, and an effort is now underway to modify the P008 telemetry database to reflect this updated limit as well.
It should be noted that this test to 90 degC was not a test to destruction, and Adcole expressed confidence that our FSS would reliably operate at the anticipated temperatures foreseeable for Chandra. In email correspondence with Adcole within the last month, they reiterated confidence in their unit. The first materials temperature of concern is for an Epoxy and does not occur until 105 degC (221 degF). Adcole also informed us that sensor drift may occur before any hard failure, and the FOT is investigating methods to detect this drift. This information can be found in FN413C.
Our current yellow limit (175 degF) is based on long-term trending, and can be raised to 181 degF without revisiting the issue. Please let Tan, or Eric, or I know if there are any further questions on these items.