16 has temperature directly measured during the test6. To predict the thermoelastic distortion based on  measured temperatures, substitute Eq. 4-6 into Eq. 1. To estimate the prediction uncertainty, substitute Eq.  7-9 into Eq. 2, where length uncertainty ( ) and temperature uncertainty ( ) is negligible. ()=∑ {[][][∆]}  +∑∆    (4) ℎ()=∑ {[][][∆]}  +∑∆    (5) ()=∑ {[][][∆]}    (6) []=∑ {[][][∆]}   +∑ [∆]     (7) [ℎ]=∑ {[][][∆]}   +∑ [∆]    (8) []=∑ {[][][∆]}      (9) Test Anomaly: MSA Mirror Locations  Shortly after beginning the test, the two detectors pointed at the mirrors mounted near the MSA started  measuring unexplained and unrepeatable angles. In addition, there was a large settling in the mirror  mounted near the upper right in Figure 15 (passive strut only side), which became apparent when the test  returned to room temperature. While the test only needs the two mirrors illustrated in Figure 15, the team  is still investigating the anomaly with the two other locations. The team believes the prime culprit has to do  with the instrumentation outside the chamber. To summarize what is going on, it is important to understand  the laser measurements. The laser goes through beam steering optics and a single beam splitter optic  before entering the chamber. The laser, detector, and optical levers are all mounted on different locations  of the optical bench outside the chamber. However, the MSA mirror instrumentation is mostly grouped  together, whereas the rotation flexure and base-plate mirror instrumentation are mostly grouped in another  location. The team believes that the MSA mirror instrumentation is not properly attached to the respective  mounts. However, to avoid disrupting the test, the investigation is on-hold until after the first mechanism  completes the thermoelastic distortion testing in early January 2018. Therefore, only the two primary flat  mirror locations illustrated in Figure 15 are discussed in this paper.   Test Results  While the test data processing is still on going for the first (of two) flight AM, the thermoelastic distortion  model represented by Equation 1 appears to be validated by the test results. In Figure 17 and 18, the first  cycle cooling-down from -40°C to -80°C is illustrated. The sample rate of the angular and temperature  measurements was 0.2 Hz. Per the pre-test calibration of the angular measurement, the angular  measurement accuracy is better than 0.1 mdeg. In addition, there is roughly 0.25-mdeg noise in the angular  measurement. PMIC takes extreme measures to minimize noise in the system, but a crude low pass filter  is still required. While a more extensive analysis could identify the correct frequency(s), a 12-point (1minute) moving average best-fit curve seems appropriate to this author. The temperature measurement  during the test is very stable. Based on thermocouple and silicon-diode calibration data, the temperature  accuracy is better than +0.2°C. At thermal steady state, the temperature measurements align to within  about 0.5°C, see Figure 187. Summarized in Table 7, the last 12-point (1-minute) test data average is  compared to the predictions, with the measured data being within the 1-sigma prediction envelope.   6The LAA bulk temperature was calculated as a linear average of several temperature measurements.  7 Although thermocouples are uniquely calibrated/serialized, PMIC only uses standard curve to simplify  implementation; PMIC controls shroud temperatures. In Figure 18, author incorporates calibration data.Figure 16. MSA Thermoelastic Distortion Variables NASA/CP—2018-219887 38