MTA Monitoring Report 08/29/25 - 09/04/25

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Radiation

Radiation Telecon Summary and SCS107 (Sept 1, 2025 6:08 pm):
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A discussion of rapidly rising radiation rates was held at the beginning of the comm that started at 4:35PM EDT today, and it was decided to safe the science instruments manually during the comm.
CAP 593A was run to initiate safing, and SCS 107 began running at approximately 244:21:09:39Z. As we are not in eclipse season, CAP 893B was run to disable SCS 29 (Eclipse load control), and the SOP_SAFE_SAFING_ACTIONS procedure executed. ACIS and HRC were verified to be in a safe state.
Current plans call for recovery load development and release during the day tomorrow, followed by review and uplink of loads during the 8:10PM comm (Sep. 02). Chandra will be in the radzone at that time and science observations will start after radzone exit at 4:43AM (Sep 03).
The team will reconvene immediately following the 9AM operations tagup tomorrow (Sep 02 Tue) to assess the development of the radiation environment and the viability of the return to science plan.
Update on Return to Science (Sept 2, 2025 10:01 am):
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Immediately following the 9AM operations tagup, status was summarized and plans for return to science reviewed (see sot_yellow_alert message of 6:07 PM yesterday, Sep 01). Radiation levels have fallen substantially and there appears to be no obstacle to implementing the return to science plan. The load (SEP0325A) was released at 9:05PM EDT yesterday for review by noon today (Sep 02) and uplink at the 8:10PM comm today. At that point Chandra is in the radzone; science observations will resume at radzone exit at 4:43 AM EDT on Wed (Sep 03). We do not currently anticipate further radiation concerns with the return to science plan, but will continue observing the radiation levels and will convene a go-nogo telecon before the 8:10 PM EDT comm this evening only if needed.

Detrended CTI

Although we prefer to quote CTI values of the cleanest data (FT <= -119.7 C, int time > 7000sec), the data that fulfills these conditions are getting rare. We now quote CTI based on temperature corrected data for Focal plane temperature <= -118.5 C).

The unit is now CTI/year not CTI/day.

ACIS Warm Pixels

We display all bad pixels that have showed up in past, and, if any, previously unknown bad pixels appeared in the last 14 days. We also list hot pixels (defined as 1000 above the average of bias background). Warm columns 509-514 are probably due to boundaries.

New definitions of warm pixels and flickering pixels (May 15, 2014). If a pixel displays the level beyond a threshold for more than 70% of the time in the past two weeks, the pixel is categorized as a "warm" pixel. If a pixel is above the threshold more than 30% of time but less than 70% of the time in the past two weeks, the pixel is categorized as a "flickering" pixel.

ACIS Focal Plane Temperature

For this period, 6 peaks are observed.

Day (DOY)	Temp (C)	Width (Days)
240.93	-98.21	1.31
241.91	-108.86	0.42
243.57	-99.06	1.07
244.55	-105.99	0.62
245.11	-111.84	0.44
245.58	-113.47	0.41

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

14 TSC moves this period

weekly average time/step	0.00130 s
mission average time/step	0.00132 s

Telemetry

New violations or new extrema are shown in blue cells.

IRUs

Gyro Bias Drift	Gyro Bias Drift Histogram

Recent Observations

Trending

This week's focus is HRC

Last reported on Jun 19.

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

• HRC Thermal

• HRC Housekeeping

If you have any questions, please contact: swolk@head.cfa.harvard.edu