Long ACIS ECS Runs: Thermal Considerations

So you want to run a long ECS run after an interruption of the science load, but you're concerned about the thermal performance of ACIS if you do.

This page addresses two solutions to modeling this situation:

[1] If the vehicle load is running, a script "ecs_thermal_model.csh" will hack the week's backstop file to resemble one in which SCS 107 was run, and then a long ECS run was started. It then runs the normal dpa_check.py program to generate a predictions page, including a table of predicted 1DPAMZT vs. time.

[2] If the vehicle load is also stopped, as in a vehicle safing action (for example, the IU Reset of Jan 6, 2015), there is a family of curves of predicted temperatures, assuming various pitch angles. For pitch angles less than 140, the DPA is no issue. For pitch angles of 140 and above, a table is given of maximum durations for ECS runs that should end under the planning limit of 35.5C.

New (May 2016)! Section 2 is rewritten to allow for off-nominal roll angles.

SECTION 1: Vehicle Load Still Running

In this section, I describe simulating the thermal performance of ACIS if there is still a vehicle load running. SCS 107 safes the science instruments, stops the instrument load, parks the ISIM at the HRC-S position, but it allows the vehicle load to continue. There will be maneuvers per the planned loads until a new load is uplinked.

There is a script, "/data/acis/LoadReviews/script/ecs_thermal_model.csh" to simulate this situation. It needs five inputs. At the moment they're edited into the script. For this reason, I suggest you copy the script to a working directory and edit it there. The inputs are:

The script requires rdb tools to run; it calls a source file to make them available.

A working directory is created, called ${week}_s107recovery.

The script looks at the backstop file found in the ofls directory for the week. It makes a copy, converts it to an RDB table for easier handling in a script, splits it into vehicle and instrument loads, and truncates the instrument load at the time of the SCS 107 run.

It then creates a few short backstop file passages. One executes the stop science commands (AA0000000, WSVIDALLDN, and a system config dump) as in the SCS 107 run. Another executes a SIMTRANS to the HRC-S position. A third sets up and starts SI mode TE_007AC, the default 6-chip mode for long ECS runs. If fewer chips are selected, the script will set up for TE_00C60 (5 chips) or TE_00C62 (4 chips). Another contains the power down commands for the end of the ECS run. Times are inserted into these passages from the input parameters (either $scs107_time, $start_time, or $stop_time).

The vehicle load, the truncated instrument load, and these four backstop passages are then concatenated, sorted on time, and converted back into standard backstop file format. This file is saved under the name CR_XXX_XXXX.backstop, which matches the wildcard used in the python code.

Two other files are also copied from the weekly ofls directory: fpsensitive.txt, and the CRM pad time file.

The script then executes the standard python temperature check programs, acisfp_check.py and dpa_check.py, creating subdirectories in the work directory called out_fptemp and out_dpa, respectively. These contain the usual thermal model outputs as generated by the LR load review script: an index.html file that makes a web page, and a pile of plots and tables.

Check the plots carefully to see that they make sense; for example that zero chips are clocking until the $start_time, and then six; that the TSCPOS is the HRC-S position of -99616; that the pitch angle changes are the same as the ones in the original load.

Have a look at the temperature profile during the proposed ECS run and see if it exceeds limits. We're mostly concerned with the DPA temperature 1DPAMZT, whose planning limit is 35.5C.

This model can be remarkably accurate (see, for example, the MAR0615 week).



For help on choosing a suitable length of run, consider the guidance in Section 2 below.

SECTION 2 -- How long can we run at a given pitch?

Revised May 2016 to include off-nominal roll angles, and new fits to the DPA (and DEA) thermal models.

If the vehicle load is stopped, or if you simply want to know how long we can run a ECS measurement at a given pitch angle, with a given number of chips, read on.

If Chandra is safed, typically the engineering staff will choose a pitch angle at which it is safe to dwell for many hours to a few days. Find out what that pitch angle is. Also ask if there's an off-nominal roll, and if so, what the angle is.

Note that there is a difference in sign between the off-nominal roll angle reported in the maneuver summary files in load review products, and that used in the thermal models.

I have run a number of cases with fixed pitch angles for 6, and 5 chips, and a starting 1DPAMZT temperature of 7.5C, which is typical of recent experience in cases of extended shutdown.

I ran a grid of pitch and off-nominal roll angles in increments of 5 degrees, from pitch=90 to 165, and off-nominal roll=-20 to +20. I ran both the DPA and the DEA thermal models. If the roll angle is close to nominal, the DPA heats faster than the DEA, so the latter may be ignored unless there's a large-ish negative off-nominal roll. Extensive use was made of John ZuHone's acispy tool SimulateECSRun().

If the roll angle is nominal, neither box gets to 35.5 C running 5 chips at any pitch angle. The DPA will get to the limit in somewhat over 40 kiloseconds for pitch angles aft of 145 runing 6 chips.

Table 1 shows the asymptotic temperature for 1DPAMZT for 5 and 6 chip cases for off-nominal-roll (ONR) of zero. Here the pitch is given in degrees, dpa_Ta_6 is the asymptotic temperature for 6 chips in degrees C, dpa_ttv_6 is the time to violation of the planning limit (35.5C) in kiloseconds, and dpa_Ta_5 and dpa_ttv_5 are the same quantities for 5 chips.

pitch dpa_Ta_6 dpa_ttv_6 dpa_Ta_5 dpa_ttv_5
90 13.42 - 12.55 -
95 13.90 - 13.03 -
100 15.57 - 13.51 -
105 18.22 - 13.99 -
110 21.09 - 16.30 -
115 23.96 - 19.17 -
120 26.83 - 22.04 -
125 29.70 - 24.91 -
130 32.56 - 27.78 -
135 33.83 - 29.04 -
140 35.10 - 30.31 -
145 36.36 55.897 31.57 -
150 37.63 42.121 32.84 -
155 37.06 46.713 32.28 -
160 36.50 53.601 31.71 -
165 35.94 66.721 31.15 -


Note that for fewer than six chips, the model predicts asymptotic temperatures less than the planning limit of 35.5C for every pitch angle. For six chips, at pitch angles of 145 or greater, 1DPAMZT will eventually exceed the planning limit. As an example, suppose that Chandra has safed, and as part of the recovery procedure, the FOT has parked the vehicle in an attitude with pitch=150 and off-nominal-roll zero. Table 1 shows an asymptotic temperature for 1DPAMZT of 37.63 C, which exceeds the planning limit of 35.5 C. Therefore, we either elect to use the 5-chip ECS run CLD file for the available duration, or to live with approaching the limit after 42.121 ksec. The ECS CAP preparation procedure adds 10.012 ksec beyond the scheduled RADMON Disable, so we subtract that amount: 42.121 - 10.012 == 32.109 ksec == 8.9 hours. We would therefore select the 8HR 6-chip CLD file, 1A_CTI6_08HR_135.cld, rounding down to the nearest hour (and available command load file). If the vehicle load is still running, I suggest taking the proposed ECS run time you get from this table and running the script in Section 1 on it, to see what a realistic vehicle load will do to change things.

In Table 2 for completeness the same information is presented for all off nominal roll (ONR) values (-20 to +20 degrees). I also present the same quantites for 1DEAMZT, with prefixes dea_.

pitch onr dpa_Ta_6 dpa_ttv_6 dea_Ta_6 dea_ttv_6 dpa_Ta_5 dpa_ttv_5 dea_Ta_5 dea_ttv_5
90 -20 12.70 - 11.44 - 11.83 - 10.77 -
95 -20 13.18 - 13.30 - 12.32 - 11.50 -
100 -20 13.67 - 17.72 - 12.80 - 13.60 -
105 -20 14.38 - 22.08 - 13.30 - 17.95 -
110 -20 17.36 - 26.37 - 13.84 - 22.25 -
115 -20 20.36 - 29.07 - 15.57 - 24.95 -
120 -20 23.38 - 31.72 - 18.60 - 27.59 -
125 -20 26.44 - 34.30 - 21.65 - 30.18 -
130 -20 29.52 - 36.84 56.553 24.73 - 32.71 -
135 -20 31.02 - 38.41 42.777 26.23 - 34.29 -
140 -20 32.54 - 39.94 36.217 27.75 - 35.81 83.449
145 -20 34.08 - 40.21 35.233 29.29 - 36.09 71.641
150 -20 35.64 87.385 40.45 34.249 30.85 - 36.32 65.081
155 -20 35.38 - 40.20 35.233 30.59 - 36.07 71.969
160 -20 35.14 - 39.92 36.217 30.35 - 35.80 84.761
165 -20 34.91 - 38.27 43.761 30.12 - 34.15 -
90 -15 12.87 - 11.11 - 12.01 - 10.44 -
95 -15 13.36 - 11.84 - 12.49 - 11.17 -
100 -15 13.84 - 15.69 - 12.98 - 11.89 -
105 -15 15.32 - 20.08 - 13.47 - 15.96 -
110 -15 18.26 - 24.43 - 14.00 - 20.30 -
115 -15 21.23 - 27.20 - 16.44 - 23.08 -
120 -15 24.22 - 29.93 - 19.43 - 25.80 -
125 -15 27.23 - 32.61 - 22.44 - 28.49 -
130 -15 30.26 - 35.26 - 25.47 - 31.13 -
135 -15 31.70 - 36.95 54.913 26.91 - 32.83 -
140 -15 33.16 - 38.61 41.793 28.37 - 34.49 -
145 -15 34.63 - 39.03 39.825 29.85 - 34.90 -
150 -15 36.12 61.473 39.41 38.185 31.33 - 35.29 -
155 -15 35.79 73.937 39.32 38.513 31.00 - 35.20 -
160 -15 35.47 - 39.21 38.841 30.68 - 35.09 -
165 -15 35.16 - 37.74 47.369 30.37 - 33.61 -
90 -10 13.05 - 10.76 - 12.19 - 10.10 -
95 -10 13.54 - 11.50 - 12.67 - 10.83 -
100 -10 14.02 - 13.60 - 13.15 - 11.55 -
105 -10 16.27 - 18.04 - 13.64 - 13.91 -
110 -10 19.19 - 22.44 - 14.41 - 18.32 -
115 -10 22.13 - 25.28 - 17.34 - 21.16 -
120 -10 25.08 - 28.09 - 20.29 - 23.97 -
125 -10 28.04 - 30.88 - 23.25 - 26.75 -
130 -10 31.02 - 33.63 - 26.23 - 29.51 -
135 -10 32.40 - 35.45 - 27.61 - 31.33 -
140 -10 33.80 - 37.25 51.633 29.01 - 33.13 -
145 -10 35.20 - 37.81 46.713 30.41 - 33.69 -
150 -10 36.62 51.961 38.36 43.433 31.83 - 34.23 -
155 -10 36.21 59.177 38.43 42.777 31.42 - 34.31 -
160 -10 35.81 72.625 38.49 42.777 31.02 - 34.37 -
165 -10 35.42 - 37.19 52.289 30.63 - 33.07 -
90 -5 13.24 - 10.42 - 12.37 - 9.75 -
95 -5 13.72 - 11.15 - 12.85 - 10.48 -
100 -5 14.57 - 11.88 - 13.33 - 11.21 -
105 -5 17.25 - 15.96 - 13.82 - 11.93 -
110 -5 20.14 - 20.42 - 15.35 - 16.30 -
115 -5 23.04 - 23.33 - 18.25 - 19.21 -
120 -5 25.95 - 26.23 - 21.16 - 22.11 -
125 -5 28.87 - 29.12 - 24.08 - 24.99 -
130 -5 31.79 - 31.99 - 27.00 - 27.86 -
135 -5 33.11 - 33.93 - 28.32 - 29.81 -
140 -5 34.44 - 35.87 80.169 29.65 - 31.74 -
145 -5 35.78 74.921 36.58 60.489 30.99 - 32.46 -
150 -5 37.12 46.057 37.28 51.305 32.33 - 33.16 -
155 -5 36.64 51.633 37.52 49.337 31.85 - 33.40 -
160 -5 36.16 60.489 37.76 47.369 31.37 - 33.63 -
165 -5 35.68 81.809 36.63 59.505 30.89 - 32.51 -
90 0 13.42 - 10.06 - 12.55 - 9.40 -
95 0 13.90 - 10.80 - 13.03 - 10.13 -
100 0 15.57 - 11.53 - 13.51 - 10.86 -
105 0 18.22 - 13.87 - 13.99 - 11.59 -
110 0 21.09 - 18.39 - 16.30 - 14.26 -
115 0 23.96 - 21.37 - 19.17 - 17.25 -
120 0 26.83 - 24.36 - 22.04 - 20.23 -
125 0 29.70 - 27.34 - 24.91 - 23.22 -
130 0 32.56 - 30.33 - 27.78 - 26.21 -
135 0 33.83 - 32.40 - 29.04 - 28.28 -
140 0 35.10 - 34.48 - 30.31 - 30.35 -
145 0 36.36 55.897 35.34 - 31.57 - 31.21 -
150 0 37.63 42.121 36.20 68.361 32.84 - 32.07 -
155 0 37.06 46.713 36.61 59.833 32.28 - 32.48 -
160 0 36.50 53.601 37.01 54.257 31.71 - 32.89 -
165 0 35.94 66.721 36.07 71.969 31.15 - 31.95 -
90 5 13.85 - 9.95 - 12.98 - 9.28 -
95 5 15.29 - 10.68 - 13.46 - 10.01 -
100 5 17.92 - 11.42 - 13.94 - 10.75 -
105 5 20.53 - 13.18 - 15.74 - 11.48 -
110 5 23.33 - 17.71 - 18.54 - 13.59 -
115 5 26.12 - 20.72 - 21.33 - 16.60 -
120 5 28.89 - 23.74 - 24.10 - 19.61 -
125 5 31.65 - 26.76 - 26.86 - 22.63 -
130 5 34.39 - 29.78 - 29.60 - 25.66 -
135 5 35.52 134.945 31.90 - 30.73 - 27.77 -
140 5 36.63 51.633 34.01 - 31.84 - 29.89 -
145 5 37.73 41.137 34.93 - 32.94 - 30.80 -
150 5 38.82 35.233 35.84 81.809 34.03 - 31.72 -
155 5 38.07 38.841 36.30 65.737 33.28 - 32.18 -
160 5 37.32 44.089 36.77 57.537 32.53 - 32.65 -
165 5 36.56 52.617 35.89 79.513 31.77 - 31.76 -
90 10 15.01 - 9.83 - 13.41 - 9.16 -
95 10 17.65 - 10.57 - 13.89 - 9.90 -
100 10 20.25 - 11.30 - 15.46 - 10.63 -
105 10 22.81 - 12.49 - 18.02 - 11.37 -
110 10 25.56 - 17.04 - 20.77 - 12.92 -
115 10 28.27 - 20.08 - 23.48 - 15.95 -
120 10 30.94 - 23.12 - 26.15 - 18.99 -
125 10 33.59 - 26.17 - 28.80 - 22.05 -
130 10 36.20 59.177 29.23 - 31.41 - 25.11 -
135 10 37.19 45.401 31.39 - 32.40 - 27.27 -
140 10 38.15 38.513 33.56 - 33.36 - 29.43 -
145 10 39.09 34.249 34.52 - 34.30 - 30.39 -
150 10 40.00 30.969 35.48 - 35.21 - 31.36 -
155 10 39.07 34.249 36.00 74.593 34.28 - 31.88 -
160 10 38.13 38.841 36.53 61.473 33.34 - 32.40 -
165 10 37.17 45.401 35.70 91.977 32.38 - 31.58 -
90 15 17.34 - 9.72 - 13.83 - 9.05 -
95 15 19.97 - 10.45 - 15.18 - 9.78 -
100 15 22.54 - 11.19 - 17.75 - 10.52 -
105 15 25.06 - 11.93 - 20.27 - 11.26 -
110 15 27.75 - 16.38 - 22.96 - 12.26 -
115 15 30.38 - 19.44 - 25.59 - 15.32 -
120 15 32.96 - 22.51 - 28.17 - 18.39 -
125 15 35.50 - 25.60 - 30.71 - 21.47 -
130 15 37.99 39.497 28.70 - 33.20 - 24.57 -
135 15 38.84 35.233 30.89 - 34.05 - 26.77 -
140 15 39.65 32.281 33.11 - 34.86 - 28.98 -
145 15 40.42 29.657 34.11 - 35.63 88.041 29.99 -
150 15 41.17 27.689 35.13 - 36.38 55.897 31.01 -
155 15 40.06 30.969 35.71 91.977 35.27 - 31.58 -
160 15 38.92 34.905 36.29 66.393 34.14 - 32.16 -
165 15 37.77 40.809 35.52 150.689 32.98 - 31.40 -
90 20 19.62 - 9.61 - 14.83 - 8.94 -
95 20 22.23 - 10.34 - 17.45 - 9.67 -
100 20 24.78 - 11.08 - 19.99 - 10.41 -
105 20 27.26 - 11.82 - 22.47 - 11.15 -
110 20 29.88 - 15.74 - 25.10 - 11.90 -
115 20 32.44 - 18.82 - 27.65 - 14.69 -
120 20 34.93 - 21.92 - 30.14 - 17.79 -
125 20 37.36 43.761 25.03 - 32.57 - 20.91 -
130 20 39.73 31.625 28.17 - 34.94 - 24.05 -
135 20 40.45 29.657 30.41 - 35.66 84.433 26.29 -
140 20 41.11 28.017 32.66 - 36.32 56.881 28.54 -
145 20 41.73 26.705 33.72 - 36.94 48.025 29.60 -
150 20 42.30 25.393 34.79 - 37.51 42.777 30.67 -
155 20 41.02 28.345 35.42 - 36.23 58.521 31.29 -
160 20 39.70 31.953 36.05 72.953 34.91 - 31.93 -
165 20 38.36 37.529 35.34 - 33.57 - 31.22 -


Tech notes:

Edited by John ZuHone to change the names from "CTI run" to "ECS run" on February 20, 2019

Richard Edgar May 17, 2016

Development work for this (section 1) was done in
/data/marple1/chandra/acis/thermal_models/recovery_thermal