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S-NPP ATMS Technical Review NASA CalVal Report

S-NPP ATMS Technical Review NASA CalVal Report. C.-H. Joseph Lyu & Ed Kim NASA/GSFC Oct. 23, 2012. 1. Introduction.

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S-NPP ATMS Technical Review NASA CalVal Report

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  1. S-NPP ATMS Technical ReviewNASA CalVal Report C.-H. Joseph Lyu & Ed Kim NASA/GSFC Oct. 23, 2012

  2. 1. Introduction In this 2nd ATMS sensor on-orbit performance report, after first post-launch review on Jan. 13, 2012, NASA Cal/Val team would focus on the review of the assigned Cal/Val Tasks, indicated in “ATMS SDR Validation OPSCON and Cal/Val Task Description” (May 24, 2011) document, listed below. Task 3 – Functional Evaluation, in Sec. 2. Task 4 – Optimal Space View Determination, in Sec. 3. (summary only) Task 8 – Scan Angle, in Sec. 4. Task 9 – Radiometric Sensitivity, in Sec. 5. Task 14 – Lunar Intrusion Mitigation, in Sec. 6. In Sec. 7, Concluding Remarks, we summarize our results, recommendations and suggestions.

  3. 2. Functional Evaluation 2-1. Task #3 Objective Evaluate that the sensor is operating as expected and was undamaged during the launch phase. Responsible Teams: NGES(Primary), MITLL(S), NASA(S) Exit Criteria: Engineering telemetry’s values are within acceptable limits. Internal Target temperature sensors & video channels are working properly. The scan synchronization agrees with radiometric data’s time stamp. 2.2. Our Analysis & Results We adopt at least four 8-min data points (randomly selected) in each month for a period of consecutive 12 months data for this study. For this task, we presented our analysis in the following slides and did not find any un-usual issues (see Figs. 2 – 1 to 2 – 12).

  4. Fig. 2-1. Engineering Telemetry Temperature Trending over 1 Year Nov. 9, 2011 ATMS operational mode started on Nov. 8, 2011, 11 days after S-NPP launch. Each point shows temperature averaged over 8 min.

  5. Fig. 2-2. Internal Hot Target PRT Temperature Trending over 1 Year Each point shows temperature averaged over 8 min.

  6. Fig. 2-3. Internal Hot Target PRT Temperature Trending over 2 Days

  7. Fig. 2-4. Radiometric Gain Trending over 2 Days, Channels 1 – 8

  8. Fig. 2-5. Radiometric Gain Trending over 2 Days, Channels 9 – 16

  9. Fig. 2-6. Radiometric Gain Trending over 2 Days, Channels 17 – 22

  10. Fig. 2-7. Dynamic Range Trending over 1 Year, Channels 1 – 8 Maximum Allowable Hot Count at 330 K is 45,150 Note Channel 1 Hot Count at 330 K is 16,100, lowest among 22 Chs & Its lowest SV Count is 3,830

  11. Fig. 2-8. Dynamic Range Trending over 1 Year, Channels 9 – 16 Maximum Allowable Hot Count at 330 K is 45,150 Note Channel 16 Hot Count at 330 K is 33,000, highest among 22 Chs & Its SV Count is 21,470

  12. Fig. 2-9. Dynamic Range Trending over 1 Year, Channels 17 – 22 Maximum Allowable Hot Count at 330 K is 45,150

  13. Fig. 2-10. Dynamic Range Sensor Specification, Channels 1 – 22 ATMS PFM 16 bits A/D 65,535, Note 65,533 may be from SD_MAIN_LOOP_POS_ERROR 45,150 33,000 Max Hot Counts at 330 K 3,830 Lowest SV Counts Based on ATMS POS, GSFC 429-00-06-03 (Figure 3-2), the allocations for the 15 bits vs. antenna brightness approximate temperature values are shown above.

  14. Fig. 2-11. ATMS Beam Position w.r.t. 8 secsSynchronization Pulse 8 sec ATMS Self Consistency Check Synchronization Timing Diagram NGES Report 14029B, March 19, 2007

  15. 2.2.1 Instrument Spec for ATMS – NGES AE-28100, 31 Jul 2002 Section # quoted below is from AE-28100 3.2.1.1.4 Scan Period The total scan period shall be 8/3 seconds +/- 1.0 msec(TBR). 3.2.1.1.5 Scan Start Synchronization The ATMS shall synchronize its scan start time with a timing signal it receives from the spacecraft. 3.2.1.1.5.1 Synchronization Signal The repetition period and other characteristics of the synchronization timing signal are provided in the External Interface Specification, AE-28102. 3.2.1.1.5.2 Scan Synchronization Accuracy The time difference between the center of beam position number one of the ATMS scan and the corresponding intended time indicated by the spacecraft timing signal shall be no greater than 0.25 msec(TBR).

  16. Fig. 2-12. ATMS Self Consistency Check Timing Difference between Two Different 8 sec Synchronization Pulses Note Scan Period check shows comparable results.

  17. 2.3. Concluding Remarks, Functional Evaluation From our presented about 1 year trending results, we find that all key engineering telemetry’s values, shelf and RFE temperatures, are very stable, within acceptable limits. Internal hot Target temperature sensors are also working properly. The ATMS self scan synchronization agrees with radiometric data’s time stamp, whose errors are within 0.25 msec. Thus, we conclude that the ATMS functional performance is in good standings. In this task we perform only ATMS synchronization self consistency check. For the CrIMSS evaluation (if required), we need to analyze both CrIS and ATMS sensors data together to determine long term synchronization timing between these two sensors.

  18. 3. Optimal Space View Determination 3.1. Task #4 Objective Determine which of the pre-determined space view angles have the least interference from the spacecraft or Earth intercept. Responsible Teams: MITLL(Co-Primary), NOAA/STAR(CP), NASA(CP) Exit Criteria: Select the least obstructed space view profile among 4 SV sectors (SPs 1 – 4) centered at 6.66o, 8.33o, 10.0o & 13.33o (below NPP+Y axis). 3.2. Our Methodology See our first review report on Jan. 13, 2012.

  19. Potential Paths if lunar moving path is perpendicular to ATMS scan plane Earth Limb SV1 SV4 SP1 SP2 SP3 SP4 SP1 SP2 SP3 SP4 NPP Platform X axis caption is used to separate different SPs. No physical meaning Earth Limb SP1 SP2 SP3 SP4 SP4 SP3 SP2 SP1 Fig. 3-1. ATMS SV FOVs NPP Platform SP1 SP2 SP3 SP4

  20. 3.3. Concluding Remarks About Optimal SP The SV measurements from SPs 1 – 4 show very stable results and their SV performances are quite comparable. We use the difference of SV1 and SV4, i.e., SV1 – SV4, from SPs 1 – 4 to be a gauge to determine which SP would be the optimal SP. We find significant differences in SV1 – SV4. The results of SV1 – SV4 from SP1 and its repeatability tests show consistently and significantly the lowest countsor the lowest impact from either s/c or earth limb infringements. In this study, all the evidences from our analysis indicate that SP1 is the optimal SP. The SP1 is currently used to optimize the ATMS on-orbit sensor performance (for detailed analysis results, please see our first review report).

  21. 4. Scan Angle 4.1. Task #8 Objective Verify that the reflector’s scan position in the science data packet matches the expected scan position. Responsible Teams: NGES(Primary), MITLL(S), NASA(S) Exit Criteria: The reflector resolver counts are within two counts (i.e., 5.493x10-3 x 2 ≈ 0.011o) of their ground measurements & the scan positions are repeatable. Note Sensor Spec: ± 0.035o. 4.2. Executive Summary From more than 11 months (one year in operational mode on Nov. 8, 2012) of ATMS scan angle performance analysis, we find that ATMS on-orbit reflector resolver counts are within the acceptable ranges. Our computed results are presented in the following slides.

  22. 4.3. ATMS Scan Angle Ideal vs. Measured As noted in the sensor spec & current & previous data, the ideal (based on Sensor Spec) scan angles, the expected (NGES) & the sensor level measured, BasePlate (BP) at 5 C, (from the Calibration Data Book, RE14029B), the s/c TVAC measured (3/23/11 10:35, BP=0C, Cold CPT), and on-orbit scan angles for the following pixels are: Table 4-1. ATMS Scan Angles in degrees Note the above values are mean scan angle, Sensor Spec: ± 0.035 deg.

  23. As found in the sensor level tests, ATMS does NOT have a perfectly symmetrical scanning (beam) pattern, because it has beam position roll angle alignment errors (see p. 27 in Cal Data Book, RE14029B). This was the main reason why the NGES expected scan angles deviated from the ideal (designed) scan angles. To demonstrate how much ATMS scan angle would deviate from the ideal and perfectly symmetrical scan angles, we adopted 104 ideal scan angles as an gauge/standard to derive the scan angle errors in the along track direction (After all, ATMS POS adopts ideal scan angles as an gauge and uses ideal angle ± 0.035o to be the requirement). The scan angle errors in pixels 1 – 48 are larger than those in pixels 49 – 96 (see next slide). The average scan angle errors for pixels 49 – 96 are very close to 0 deg.

  24. Fig. 4-1. ATMS On-orbit Scan Angle Measurement, Pixels 1 – 48 Sensor Spec: ± 0.035 deg Scan Angle Mean Errors for Pixels 1 – 48 are ≈ -0.01o

  25. Fig. 4-2. ATMS On-orbit Scan Angle Measurement, Pixels 49 – 96 Sensor Spec: ± 0.035 deg Scan Angle Mean Errors for Pixels 49 – 96 are ≈ 0.0o Those for Pixels 61 – 64, 73 – 76, 81 – 88 are ≈ -0.0025o

  26. Fig. 4-3. ATMS On-orbit Scan Angle Measurement for Pixels 1, 24, 48, 49,73,96, & 101(Hot#1), 104(Hot#4) Sensor Spec: ± 0.035 deg

  27. 4.4. Concluding Remarks 1/2 From the measured data presented in Table 4-1 and Figures 4-1 – 4-3, the scan angle errors are sometimes as large as -0.045 deg (only in the warm target FOVs), which are beyond the beam error limits, +/-0.035 deg. Nevertheless, they are measured from the same (uniform) warm target. Moreover, the errors from the warm target FOV # 1 show positive errors and those from the warm target FOV # 4 show negative errors (see Fig. 4-3). This implies that the 4 FOVs for K/Ka bands were designed to view very close to the complete warm target. Considering that we use also the average of 4 FOVs, we find that the warm target calibration data should be mostly ok. To make sure that we have good calibration data, it is necessary to monitor the scan angle errors from the internal calibration target constantly. As to the scan angle errors from the EV pixels 1 – 96, we find that the errors are quite small in the along scan direction. As noted in Figures 4-1 – 4-3, the scan angle errors in pixels 1 – 48 are larger than those in pixels 49 – 96. We suggest that we use pixel 49 to perform geolocation validation, if applicable.

  28. 4.4. Concluding Remarks 2/2 The NGES report examined scan angle errors only for the Earth View (pixel) positions 1-96. Here we examine also scan angle errors around the internal calibration view positions. Since the Space View (SV) port faces a wide cold space scene, even with a large scan angle error, e.g., 1 deg., there would have no impact to the cold scene data (unless s/c reflections are an issue). In this study, thus we did not check on SV scan angle error. The internal calibration target, however, has a limited size, so we pay more attention to the scan angle error around the internal (warm) target. Based on Report 13807 Rev. B, ATMS Instrument Operation and Maintenance Manual, page 34, the size of WG band warm target is 4.9 x 5.232 deg (elliptical), that of KV warm target is 7.9 x 8.425 deg. There are 4 FOVs that scan across the warm target. To compute the tolerance of the scan angle for the G bands (FOV=1.11o), we find that 5.232 –4.44 = 0.792 deg. Namely, the tolerance for G bands should be +/-0.396 deg. For the W band (FOV=2.22o), the tolerance is 5.232 –5.55 =-0.318deg, namely, no tolerance. For the V bands (FOV=2.22o), the tolerance is about +/- 1.4375 deg. For the K/Kabands (FOV=5.20o), 8.425 –8.53 = -0.105 deg , i.e., no tolerance. Nevertheless, although there is NO scan angle error tolerance for W and K/Ka bands, yet the warm targets are in near fields, the NPP/ATMS warm target sizes are not an issue. After inspecting the warm pixel counts, we find no issue associated with warm target scan angles.

  29. 5. Radiometric Sensitivity 5.1. Task #9 Objective Evaluate the on-orbit radiometric sensitivity (NE∆T). Responsible Teams: NGES(Primary), MITLL(S), NASA(S), NOAA/STAR(S) Exit Criteria: On-orbit measurements of NE∆T are lower than the requirements and any deviations from ground measurements are investigated and recorded. 5.2. Our Methodology Temperature sensitivity (NET) is defined in GSFC 429-00-06-03 as the standard deviation of the radiometer output temperature in degrees Kelvin (K) when the antenna is viewing a 300 K uniform and stable target. We adopted two different approaches, (1) NEΔN / gain and (2) NGES System Calibration Test Procedure (AE-26842C, Sec. 7-4), for this study. To compute for NEΔN / gain, our modified equations are slightly different than those in “NPP_ATMS_SDR_OPSCON_Version3_May 24_2011.docx”, p. 50, whose quoted equations are from NGES RE-13676, ATMS In-flight Activation & Checkout Plan. Both (1) and (2) are expected to result in comparable results.

  30. Fig. 5-1. Radiometric Sensitivity Measurement, Channels 1 – 8 Based on NGES Test Procedure, AE-26842C

  31. Fig. 5-2. Radiometric Sensitivity Measurement, Channels 9 – 16 Based on NGES Test Procedure, AE-26842C

  32. Fig. 5-3. Radiometric Sensitivity Measurement, Channels 17 – 22 Based on NGES Test Procedure, AE-26842C

  33. 5.3. Concluding Remarks Our analysis indicates that both approaches (1), see backup slides, and (2) show comparable NEΔTs. From our 1 year trending of ATMS on-orbit radiometric sensitivity, see Figs. 5-1, 5-2 & 5-3, we find that on-orbit (long term trending) NE∆Ts are lower than the requirements and meet the sensor specification.

  34. 6. Lunar Intrusion Mitigation 6.1. Task #14 Objective Determine a routine procedure for dealing with lunar contamination of the cold space calibration target. Responsible Teams: NASA(Co-Primary), NOAA/STAR(CP) Exit Criteria: A lunar contamination mitigation plan is prepared and executed. 6.2. Background From two worst lunar intrusion cases, e.g., one on Dec. 5, 2011, at 6:41, & the other on May 1, 2012 centered at 10:42:10, we find that all 4 SV pixels got contaminated for K/Ka bands, and only 1 SV pixel was free of lunar contamination for V, W and G bands. If we adopt previous (NG established) plan to abolish SDR/TDR processing when we have less than 3 SV pixels free of lunar contamination, then at 6:41 we would lose about 25 min for K/Ka bands (Chs 1 & 2) data and lose about 7 – 12 min worth of data for all other bands. Then from Dec. 3 to Dec. 5, 2011, we would lose, at most, about 10 hours worth of TDR, calibrated SDR, Re-map SDR, and EDR data products during this time. Some lunar intrusion cases are presented in the followings.

  35. Fig. 6-1. Lunar Intrusion to SV from Apr. 30 to May 1, 2012 Note that Lunar intrusion moves from SV1 to SV2, SV3, SV4, …, etc.

  36. Fig. 6-2. Lunar Intrusion to SV on May 1, 2012 centered at 10:42:10 For K/Ka bands, NO good SV. For V/W bands, SV4 is good for data processing. Another worst lunar contamination lasted for about 25 min, for K/Ka bands.

  37. Fig. 6-3. Lunar Intrusion to SV on May 1, 2012 centered at 10:42:10 For G bands, SV4 is good for data processing. For V/W/G bands, another worst lunar contamination lasted for about 7 min.

  38. Fig. 6-4. Lunar Intrusion to SV on May 1, 2012 centered at 12:23:10 For K/Ka bands, SV4 is good. For V/W bands, two SV3 & SV4, are good .

  39. Fig. 6-5. Lunar Intrusion to SV on May 1, 2012 centered at 12:23:10 For G bands, three SV2, SV3 and SV4 are good for data processing. Use slide # 19 to explain about the best lunar intrusion mitigation plan

  40. 6.3. Solutions And Recommendations • There are four potential methods of lunar intrusion mitigation: • We simply ignore pixels that are corrupted by the moon, but we adopt at least one (if applicable) of the four available pixels is unaffected, andWe correct for the lunar perturbation using the viewing geometry and a radiometric model of the moon. • We just use “Good” pixels (even one or their average, if applicable) to substitute for the mean SV in the current data processing codes. • Processing system could bridge across samples where no calibration can be done due to rejected cold-cal (SV) views. Namely, we can use a lunar radiative model and use it to correct contaminated SVs. On Aqua, the “bridge across gaps” method is adopted. From our functional evaluation in Sec. 2, we find that the gain is quite stable to perform this approach. • As demonstrated in Fig. 3-1, see p. 19, we should be able to switch between different SPs. For instance, if the moon would scan across SP1, then we could choose SP4 to avoid the lunar contamination. As indicated by NGES, the stability is not an issue to perform this one.

  41. 7. Concluding Remarks/Recommendations Based upon our assessment on ATMS functional evaluation, scan angle and radiometric sensitivity, we find that all key engineering telemetry’s values, shelf and RFE temperatures, internal hot Target temperatures, and the sensor performance are very stable, and they meets the sensor specifications. The ATMS self scan synchronization agrees with radiometric data’s time stamp, whose errors are within 0.25 msec. For the CrIMSS evaluation, if other teams have not done so, then we would need to analyze both CrIS and ATMS sensors data together to determine long term synchronization timing between these two sensors. For lunar intrusion mitigation plan, we would recommend to adopt method (4). Namely, when moon would appear in the SP1, we can select SP4 during those lunar contamination periods, so that we would eliminate all the lunar intrusion issues.

  42. In the current IDPS processing system, if we don’t have any lunar intrusion mitigation plan, when lunar contamination occurs, the affected cold space views are not used in the calibration. But SDRs are still generated for the good EV data using the uncontaminated calibration data.  In other words, SDRs are still being produced (But how do we do it? No clear statements in current ATMS OAD & ATBD) when moon contamination occurs. Not just for lunar intrusion, there are a number of other quality flags in the SDR product that the users may want to know. It could be beneficial to add the QF description in the users manual (Dequi, 8/28/2012 email). For improving geolocationmatching between ATMS/CrIS, compared to ATMS/CrIS 0 sec sync (no sync timing adjustment), we find that ATMS pixel 47/CrIS FOR 15 sync would reduce the geolocation(two scanning patterns) matching errors from 69.4” to 3.60”, or 2.141 km to 0.111 km. Our study indicates that ATMS SDR data product is ready to be declared in provisional maturity status, if no other pending issues are applicable.

  43. Acknowledgements On-orbit ATMS data reader and some analysis codes were initially developed by MIT-LL. JPSS DPA/DPE has extensive assistances on post-launch ATMS cal/val tasks. JPSS/NPP MOT teams have assisted us in performing ATMS on-orbit sensor operations and maneuver implementations. Specifically, we would also like to thank all ATMS SDR and CrIMSS EDR teams for working together on the ATMS data related issues, processing and cal/val tasks.

  44. Backup Slides

  45. Fig. B-1. Use NEdN / gain to determine NEdT, Channels 1 – 8 Approach (1), see page 29 for details. Compared it with p. 30.

  46. Fig. B-2. Use NEdN / gain to determine NEdT, Channels 9 – 16 Approach (1), see page 29 for details. Compared it with p. 31.

  47. Fig. B-3. Use NEdN / gain to determine NEdT, Channels 17 – 22 Approach (1), see page 29 for details. Compared it with p. 32.

  48. Jan 13, 2012 Review slide, Fig. 6 – 3 Fig. B-4. Lunar Intrusion to SV on Dec. 5, 2011 centered at 06:41:15 Lunar φ = -57.48o, moon center is ≈ 0.15o from SV2 FOV center For K/Ka bands, NO good SV. For V/W bands, SV4 is good for data processing. The worst lunar contamination lasted for about 25 min, for K/Ka bands.

  49. Jan 13, 2012 Review slide, Fig. 6 – 4 Fig. B-5. Lunar Intrusion to SV on Dec. 5, 2011 centered at 06:41:15 Lunar φ = -57.48o, moon center is ≈ 0.15o from SV2 FOV center For G bands, SV4 is good for data processing. For V/W/G bands, the worst lunar contamination lasted for about 7 – 12 min.

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