TES Algorithm Status. Helen Worden

Transcription

1 TES Algorithm Status Helen Worden

2 Outline TES Instrument System Testing Algorithm updates One Day Test (ODT) 2

3 TES System Testing TV3-TV19: Interferometer-only thermal vacuum testing (11/00 to 5/02) Achieved nearly optimal modulation. ST1: First integrated system test (8/17/02-8/28/02) The interferometer alignment was considerably different from interferometer only testing. High scan-to-scan radiometric instability. Larger than expected ice build-up caused significant signal loss. Approx. 150 minor issues identified. All data processed by Cal-SIPS through L1A. ST2: Implemented some fixes, further characterization (10/17/02-11/03/02) Confirmed radiometric instability due to ASICS electronic filters. Bypassing filters eliminated variability at the expense of more noise (~3x). Interferometer alignment found to depend on temperature and to drift significantly with time. Detector 1A, pixel 1 started oscillating. Pixel channel shifts still observed. 3

4 TES System Testing (cont.) ST3: Interferometer bolts loosened to simulate kinematic mount (12/04/02-12/17/02) Better initial alignment, but still observed drift. Tested detector de-icing. Higher signals and more favorable shear observed at higher interferometer temperatures. Verified fix (shorting) to 1A pixel 1. Lose pixel, but not entire array. ST4: Shape Memory Alloy (SMA) mounts installed + Pre-vibe baseline (1/26/03-2/17/03) SMA mounts may have improved initial alignment. Mechanical systems analysis together with engineering model beam splitter test test point towards friction between KBr beam splitter and RTV as possible cause of drift. ST5: Instrument Calibration (3/18/03-4/13/03) Radiometric: linearity, gain, noise, onboard radiometric source (OBRCS) Spatial: field of view (FOV) response, detector co-alignment, OBSCS Spectral: Instrument line shape (ILS) from gas cell and CO 2 laser 4

5 Signal loss due to ice build-up (over 10 days) 5

6 TES System Test Gas Cell Measurements 6

7 Radiometric Calibration Example 220K Source 7

8 Radiometric Calibration Example 300K Source 8

9 Calibration Accuracy Current status analysis in progress ST5 Run 513 (300 K external BB) Filter # scans NE T Sys. Err. (K) averaged (K) T(extBB)- T(best fit) 2B B B A A A

10 New L1 Algorithms To address issues found in System Testing L1A Channel shifting determination: mean value algorithm L1B Shear determination algorithm Ice buildup detection Potential need for dynamic frequency correction if interferometer shear is not stable post-launch. 10

11 Impacts of Instrument Characterization To L2 Retrievals Increased noise because electrical filters could not be used. Increased noise degrades retrieval precision and increases computational burden because larger spectral window frequency ranges must be selected to optimize information content. Other instrument model parameters such as FOV and ILS were characterized and default values were replaced with real ones. 11

12 Estimated O 3 Errors from Microwindow Selection Pre- system testing noise Post system testing noise 12

13 One Day Test (ODT) Science Objectives Test L2 algorithm accuracy, robustness & performance for a large number of retrievals Nadir, 3504 Limb targets Determine which retrieval diagnostics and visualization methods will be most useful for monitoring science data quality & instrument performance. Evaluate statistical accuracy of error estimates as compared to known errors (true-retrieved). Can t do this with real data. Determine if target scene selection would significantly improve performance by reducing the number of iterations required. 13

14 TES One-Day Test Input and Assumptions Simulated TES spectra were created using profiles sampled from MOZART3 (NCAR) model data. MOZART resolution is 2.8 x2.8 with 66 vertical levels (0-140 km). MOZART3 was driven by WACCM met. fields; data are for the Oct. 2 day of an arbitrary year. (WACCM = Whole Atmosphere Community Climate Model, from NCAR) No clouds or aerosols. Results from this 1 st test will be a baseline for later tests. Retrieved surface T, but not surface emissivity. Noise added to simulations is from instrument characterization. TES Filter ID Frequency Range (cm -1 ) Nadir NESR (nw) 16 pixel avg. Limb NESR (nw) 2B1 1B1 1B2 2A1 2A4 1A

15 One Day Test Nadir Results Ozone: True State Retrieved Retrieved - True Ozone VMR (ppmv) 15

16 Nadir O 3 Error Comparison for the One-Day Test Comparison of initial uncertainty, mean ± 1σ actual errors (retrieved true), and estimated errors for One-Day Test Ozone retrievals. Fractional errors for O 3 (log VMR) retrievals 16

17 Current / Future Work Updating the ATBD (now at V1.2, V2.0 by 10/2003) Preparation for post-launch mayhem (a.k.a. commissioning) Aura Intercomparisons Limb 2-D retrieval and characterization - uses 3 limb measurements to retrieve 4 profiles over 6 o latitude. Cloud top pressure retrieval - include lower bound pressure in retrieval vector Retrievals with transmissive clouds/aerosols using proxy gray-body layers. 17

18 BACK-UP SLIDES 18

19 L1 & L2 ATBD Status Updates for At-Launch Versions Level 1 ATBD Inclusion of L1A. Channel shift correction & Geolocation algorithms. New algorithms to handle instrument effects discovered during the system tests (ST1-ST5). Inclusion of real data from TES. Level 2 ATBD Updates to retrieval strategy, error analysis Inclusion of more simulation results. 19

20 Level 1 ATBD Revisions 10/99 V1.1 (L1B ATBD) on Interim algorithm changes/additions are documented in DFMs (Design File Memos) that will be incorporated in ATBD. Calibration Report V1 ready 9/29/2003. V2.0 ready 10/30/

21 Mission Critical Analysis On-Orbit Calibration Interferogram and spectral analysis (using L1A Tier 1 products), similar to system test analysis will need to provide direction to Mission Ops while tuning the interferometer. Analysis of special calibration data (L1A Tier 1 products) on-board spatial calibration source radiometric performance dark filter positions Determine on-orbit environmental impacts to system performance e.g. sun angle influence on instrument offset radiance. Need Tier 2 data, i.e. geolocation. Algorithm prototyping as needed 21

22 L1A IFGMs X TES L1B Post-launch Analysis Flow (Nadir) Nadir 1B2 Clear ocean scene w/reliable SST Calibration w/initial or updated parameters Identify cloud free Ocean scene Offset dependence analysis e.g. w/latitude, to determine cal. avg. strategy Check on-orbit variable BB cal. compare w/ground Verify spatial cal. (pixel positions) compare w/ground Compare w/ AIRS and model radiance Nadir 2B1 Freq. calibration w/averaged data line positions compared to model Compare w/ AIRS, model radiance and 1B2 Nadir 2A1 Updated OSPs Updated OSPs e.g. Freq. Cal. Coeff. Updated OSPs Compare w/ AIRS, model Radiance & 1B2 Nadir 1A1 X X n ok? X X Updated OSPs Compare w/ model radiance X y L1B Radiances 22

23 Analysis Flow Legend X start point decision data procedure Manual operation stored data preparation 23

24 Daily Health & Quality Assessment Examine Standard Plots Diagnostic quantity vs. time for data trends, esp. Tier 1 diagnostic products that are related to instrument performance can affect Mission Ops. Global maps of L1B brightness temperatures Global maps retrieval diagnostics, e.g. χ 2 Curtain plots for profiles Fractional signal loss from ice build-up

25 Mission Essential Analysis Diagnose Failed Retrievals Case-by-case basis examine profile and radiance residuals Determine whether mechanical or physics/chemistry algorithm failure Additional algorithm development Retrieval Validation Activities Process special correlative TES observations coordinated with field campaigns Data comparisons Q.A. Research Products, (e.g. non-standard product species) Global Survey data and Special Observations May become standard products 25