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CALIBRATION AND PERFORMANCE OF THE HAMSR INSTRUMENT DURING THE NASA GRIP CAMPAIGN

This article discusses the calibration and performance of the HAMSR instrument during the NASA GRIP campaign, including the thermal environment, external targets, nominal calibration, receiver temperature calibration, and overall instrument performance.

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CALIBRATION AND PERFORMANCE OF THE HAMSR INSTRUMENT DURING THE NASA GRIP CAMPAIGN

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  1. CALIBRATION AND PERFORMANCE OF THE HAMSR INSTRUMENT DURING THE NASA GRIP CAMPAIGN Boon Lim*, Shannon Brown, Richard Denning, Pekka Kangaslahti, Bjorn Lambrigtsen, Jordan Tanabe, and Alan Tanner Jet Propulsion Laboratory *Contact : Boon.H.Lim@jpl.nasa.gov

  2. Outline • HAMSR Overview • Genesis and Rapid Intensification Processes (GRIP) Campaign • Data System • Thermal Environment • External target – Stability, Gradients, Reflection • Nominal Calibration (V0) • Receiver Temperature Calibration (V1) • Calibration Comparison (V0 vs V1) • HAMSR Performance • Summary IGARSS 2011

  3. HAMSR Overview • High Altitude MMIC Sounding Radiometer (HAMSR) • 3 Sounding Bands (55, 118 and 183 GHz) • 25 total channels • Oxygen and Water Vapor Bands for Profiling • Cross-Track Scanner with Ambient/Hot External Calibration Targets • Product of ESTO (IIP, ACT and AITT) • Entering 15th Year • Participated in 5 Campaigns • Integrated on 3 Aircraft IGARSS 2011

  4. GRIP Campaign • Genesis and Rapid Intensification Processes Campaign • 5th Coordinated Hurricane Field Campaign Since 1998 • NOAA, NSF and the AF • From August to September 2010 • DC-8 (9), Global Hawk (4) and WB-57 (2) • Approximately 300 flight hours • Hurricane Frank (Pacific), Tropical Storm Matthew (Atlantic), Hurricanes Earl and AL-92/Karl (Atlantic) • Global Hawk Stationed at Dryden • Over 120 Flight Hours for the Global Hawk • 20 Eye Overpasses Hurricane Karl (~13 Hours) • Typical flight duration 24 Hours IGARSS 2011

  5. GRIP Flights Earl 09/02/2010 Karl 09/16/2010 Matthew 09/23/2010 Frank 08/28/2010 AL92 09/12/2010 IGARSS 2011

  6. HAMSR Imagery During GRIP Hurricane Earl 2010

  7. Hurricane Matthew Platform Report – Scott Braun 7/29/2011 IGARSS 2011 7

  8. HAMSR GRIP Ground Data System Commanding Data downlink netCDF L1B files GHOC JPL Hurricane Portal HAMSR website quick look images RTMM HAMSR ground data processor

  9. HAMSR RTMM Display for GRIP HAMSR software upgraded after GRIP to provide real-time imagery over Iridium Successfully tested during 2011 WISPAR campaign

  10. Thermal Environment • HAMSR Sits in an Unpressurized Pod • RF Section is Thermally Insulated with Styrofoam • Temperature Controlled Heaters on the RF Plates • Thermistors Available Across the Instrument • RF Components (RF/IF LNAs, Mixers), RF Plate Temperatures, Motor, Power Supply, Digital System, Computer, Etc • Fans for Circulation of Air • On Runway if Temperatures Exceed a Threshold • At Flight Altitude (~17 km) • Temperature Typically -150C 7/29/2011 IGARSS 2011 10

  11. WISPAR 2011- Thermal Environment 7/29/2011 IGARSS 2011 11

  12. External Target - Stability • Thermistors Embedded in Targets • Ambient Target Drifts Freely • Rate of Change 6-7oC/Hour • Hot Target Held at ~68oC • Oscillation at 120 Second Period, 0.01K< IGARSS 2011

  13. External Target - Gradients • Gradients Across the Target Pixels • Typically Monotonic • Magnitude Under 0.3K • Easily Mitigated with Averaging IGARSS 2011

  14. External Target - Reflections • Standing Waves Setup in the Middle of the Target • Despite Low Return Loss Material (~35 dB) • Only in Several Frequencies • Remove Central Pixels IGARSS 2011

  15. Initial Processing • Moving Average of the Hot and Ambient Counts • Period of the Heating Oscillation (~110 Seconds) • Time ‘Shift’ in Ambient Counts • Account for linear time drifts • Calculate Per-Scan Gain • Gain = (CHot – CAmb)/(THot – TAmb) [C/K] • Flag Unusable Pixels (-2) • Insufficient Separation of the Hot and Ambient Targets • Differential Temperatures on Targets, 5xNEDT • Differential Gain, Threshold (empirical) IGARSS 2011

  16. Nominal Processing • Moving Average of Gain • Calculate Antenna Temperature • TA = (Ct – CAmb)/Gain + TAmb • Standard Calibration Stratagy • Gain Drifts/Jumps Distributed in the Averaging • Incorrectly Processes ‘Good’ Data 7/29/2011 IGARSS 2011 16

  17. Receiver Temperature Calibration • Calculate Receiver Temperature • TRx = CAmb/Gain - TAmb • Smooth Receiver Temperature • Calculate Gain (from Hot Target) • GHot = CHot/(TRx+CHot) • Calculate Gain (from Ambient Target) • GAmb = CAmb/(TRx+CAmb) • Average Gain • Gain = (GHot+GAmb)/2 • Calculate Ta • TA = (Ct – CAmb)/Gain + TAmb 7/29/2011 IGARSS 2011 17

  18. Comparison – Gain Smoothing 7/29/2011 IGARSS 2011 18

  19. Comparison – Spikes 7/29/2011 IGARSS 2011 19

  20. Comparison – Robustness 7/29/2011 IGARSS 2011 20

  21. Flag Marginal Pixels • Pixels that Exhibit Larger than Expected Noise • Temperature is Over 3.5x NEDT • Empirical Value for Each Channel • For End-Product Users 7/29/2011 IGARSS 2011 21

  22. Marginal Pixels 7/29/2011 IGARSS 2011 22

  23. Flag Marginal Pixels Second Check Receiver Temperature Calibration Close to the Theoretical Values for Noise 7/29/2011 IGARSS 2011 23

  24. Instrument Performance • As Derived from the Data • Hurricane Karl • 55 GHz Performs the Poorest • Legacy Hardware • Upgrade in Progress (~4dB) • 118 GHz and 183 GHz Upgraded During AITT • Performance is as Expected from the Receiver Temperatures • 99.9% Up-Time • 1 Channel Dropped Out for 3 Hours 7/29/2011 IGARSS 2011 24

  25. Summary • External Targets Well Characterized • HAMSR Successfully Participated in GRIP Campaign • Data System Utilized High Bandwidth Link (‘Real-Time’) • Utility was Immediate in Directing the GH Flight Path • Calibration Methodology Relies on Stability of Receivers • Front End LNAs vs Entire Gain Chain • HAMSR Receivers as a System Perform to Measured Receiver Temperatures • WISPAR Campaign Had Coincident Dropsondes • Absolute Calibration Comparison Pending • Instrument calibration and characterization (Brown et al., TGRS, in press) 7/29/2011 IGARSS 2011 25

  26. Backup Slides • HAMSR Timeline • HAMSR Block Diagram • External Target Construction • Pre-Flight Evaluation • Allan Variance LN2 Stare • GRIP – Agency Coordination • Danielle, Earl and Fiona IGARSS 2011

  27. HAMSR Timeline IGARSS 2010=1

  28. HAMSR Block Diagram IGARSS 2011

  29. External Target - Construction • Pyramidal Blackbody Calibration Targets • Ambient and ~680C • Commercial Product with -50dB Return Loss Spec • Heavy Aluminium Coated with a Ferrite Loaded Epoxy Absorbing Material • 16x12 cm Area, 4 cm Long Pyramids, 1 cm Apart at Tips • 4 Thermistors Embedded in Targets at the Tips • Insulated in Styrofoam • ~35dB Return Loss IGARSS 2011

  30. Pre-Flight Evaluation – Scan Bias • Within the field of view, minimal bias in the various channels • 50 GHz channels: • Bias < 0.5 K for -45o < θ < 45o • 118/183 GHz channels: • Bias < 0.25 K for -45o < θ < 45o IGARSS 2011

  31. Allan Variance LN2 Stare 7/29/2011 IGARSS 2011 31

  32. GRIP – Agency Coordination 7/29/2011 IGARSS 2011 32

  33. Danielle, Earl and Fiona IGARSS 2011

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