Capabilities of NIST SIRCUS for Calibrations of SSI Vis-IR Instruments

Transcription

1 Capabilities of NIST SIRCUS for Calibrations of SSI Vis-IR Instruments Steve Brown National Institute of Standards & Technology Gaithersburg, MD

2 Answer: Ask LASP folks In 2005/2006, SIRCUS measured a SIM brassboard slit scatter function & ESR responsivity with Erik Richard, Jerry Harder and Colleagues from Laboratory for Atmospheric and Space Physics (LASP), Boulder CO Spectral Irradiance Monitor (SIM) on SORCE SIM is a Fèry prism spectrometer; only one optical element is needed to disperse and focus the light onto four photodiode detectors and an electrical substitution radiometer (ESR). Solar Spectral Irradiance (SSI) Variations Workshop 2012 February 2

3 SIM Brassboard Slit Scatter Function Grey lines ray trace model J. W. Harder, G. Thuillier, E. C Richard, et al., The SORCE SIM Solar Spectrum Comparison with recent observations, Solar Phys. 263, 3-24 (2010). Solar Spectral Irradiance (SSI) Variations Workshop 2012 February 3

4 ESR Efficiency Results Net result was that the radiometric response of the SIM instrument needs to be increased by a factor of across the 258 nm to 1350 nm regime. J. W. Harder, G. Thuillier, E. C Richard, et al., The SORCE SIM Solar Spectrum Comparison with recent observations, Solar Phys. 263, 3-24 (2010). Solar Spectral Irradiance (SSI) Variations Workshop 2012 February 4

5 SSI Workshop 1, September 2006 Worthwhile repeating the measurements Solution: NIST loaned LASP an L-1 Stnds&Technol cryogenic radiometer and a Traveling SIRCUS system Contact: Dave Harber, LASP, dave.harber@lasp.colorado.edu Solar Spectral Irradiance (SSI) Variations Workshop 2012 February 5

6 NIST SIRCUS Capabilities for SSI Measurements in the Reflected Solar Regime Introduction to SIRCUS What do we need the facility to do? Available irradiance Uncertainty requirements Can SIRCUS achieve irradiance levels and uncertainties required for SSI climate change sensors? Solar Spectral Irradiance (SSI) Variations Workshop 2012 February 6

7 Facility for Spectral Irradiance and Radiance responsivity Calibrations using Uniform Sources Develop broadly tunable laser systems to replace Fixed frequency laser systems for scale derivations Lamp-monochromator systems for detector calibrations NIST Radiant Flux (Power) Uncertainties Extend the spectral region of low uncertainty; Extend to irradiance and radiance responsivity Solar Spectral Irradiance (SSI) Variations Workshop 2012 February 7

8 Coupling Tunable Lasers with Cryogenic Radiometers Scale Derivations Historically QE measured at a few points and interpolated using a physical model developed at NIST Developed for the 405 nm to 920 nm spectral region Uncertainties tend to be much larger outside this spectral region With SIRCUS, we can 1. directly measure and fit the quantum efficiency of Si trap detectors 2. extend the spectral coverage beyond the Si region Solar Spectral Irradiance (SSI) Variations Workshop η e λ [nm] EQE Wavelength (nm) 2012 February 8

9 SIRCUS Lasers determine the spectral coverage Detectors determine the uncertainties ultimately achievable Solar Spectral Irradiance (SSI) Variations Workshop 2012 February 9

10 Does SIRCUS provide enough Irradiance? Optical Power: Lasers v. Lamp Monochromator Systems SIRCUS 10 NIST Lamp-Monochromator Monochromator Output Flux (Power) [µw] Argon Mini-Arc 420 nm 100 W Quartz-Halogen Lamp nm 600 nm 985 nm nm 1385 nm February Solar Spectral Irradiance (SSI) Variations Workshop Wavelength (nm) 1000 mw 1 µw SIRCUS: 10 6 times more power 10

11 Does SIRCUS provide enough Irradiance? SIRCUS irradiance levels (in a 2 inch beam) compared with solar levels (in a 10 nm bandpass) 1.E+04 1.E+03 E-490 (10 nm bp) v SIRCUS (5 cm diameter beam) Spectral Irradiance W*m -2 *micron Linear Plot ETR ASTM E-490 vs. Wehrli WMO Irradiance /(W/m 2 ) 1.E+02 1.E+01 1.E+00 1.E-01 1.E-02 1.E-03 1.E Wavelength /nm Wavelength micrometers 2012 February Solar Spectral Irradiance (SSI) Variations Workshop 11

12 Laser Can SIRCUS achieve the required uncertainty? How are the uncertainties validated? SSI Uncertainty Requirements for Climate Studies NPOESS SIM instrument: relative uncertainty of 0.01 % and a combined absolute Uncertainty of < 0.5 % from 200 nm to 2400 nm. Erik Richard, et al. TRUTHS Requirements for SSI: < 0.1 % (k=1) CLARREO: solar reflected radiation 0.3 % (k=2) SIRCUS Propagated Uncertainties (Si region) Reference Detector V % (k=2) Distance Aperture Area Uniformity exit port (radiance) ref plane (irradiance) Detector Responsivity I-V Gain factor 2012 February Solar Spectral Irradiance (SSI) Variations Workshop 12

13 Validating SIRCUS Uncertainties Development of Imaging Radiometers Howard Yoon, David Allan, & colleagues, NIST Gold-point Blackbody Advanced Pyrometer February 13 Solar Spectral Irradiance (SSI) Variations Workshop

14 Radiance Responsivity of the Absolute Pyrometer 1 (AP1) and Spectral Radiance from the Gold-Point Blackbody ( ) (, ) ( ) S A= L λ TRλ dλ Planck Radiance Responsivity, S L [ A/W/(cm 2 sr) ] K Wavelength [ nm ] Spectral Radiance, L [ W/(cm 2 sr) nm ] Howard Yoon, NIST Solar Spectral Irradiance (SSI) Variations Workshop 2012 February 14

15 Melting and Freezing Cycles of the Gold-point Blackbody T AP1 [ K ] AP-1 Measurements Time [ min ] 2012 February Solar Spectral Irradiance (SSI) Variations Workshop Howard Yoon, NIST 15

16 Temperature Determination of a Gold-point Blackbody Source 1.007x x K K Radiometric Photocurrent [ A ] 1.005x x x x x x x T 0.15 % (k=2) in Radiance Resp. 120 mk T 90 Temperature [ K ] T 90 =International Temperature Scale of 1990 Solar Spectral Irradiance (SSI) Variations Workshop H. Yoon, NIST 2012 February 16

17 Keith Lykke, Leader SIRCUS Staff Acknowledge: SIRCUS Personnel Steve Brown, Ping Shaw, Allan Smith Contributors Conclusions SIRCUS has both the flux levels and the uncertainties (from 210 nm to 1.6 µm) required to support characterization and calibration of Solar Spectral Irradiance sensors Demonstrated success looking at a SIM Breadboard instrument at NIST and work currently underway at LASP George Eppeldauer, Transfer Standard Detectors Joe Rice & Jeanne Houston, Primary Optical Watt Radiometer (POWR) Colleen Jenkins, Mike Lin, Technical Support Solar Spectral Irradiance (SSI) Variations Workshop 2012 February 17

18 Things Dave Harber has been up to at LASP with SIRCUS lasers and L-1 cryo radiometer Previously: Used the SIRCUS lasers to measure the flight TSIS SIM Fery prism transmission from nm This is a measurement of the Fresnel reflection and Aluminum reflection losses in the Fery prism Using the SIRCUS lasers and the Cryogenic Radiometer, we calibrated the TSIS SIM electrical substitution radiometer (ESR) from 211 nm to 2400 nm Currently: Using the SIRCUS lasers to calibrate the wavelength scale of the SIM flight instrument and to measure the instrument response function as a function of wavelength and pointing, from 211 nm to 2400 nm Up Next: Use the SIRCUS lasers and the Cryogenic Radiometer to calibrate the end-to-end radiometric sensitivity of SIM, from 211 nm to 2400 nm Solar Spectral Irradiance (SSI) Variations Workshop 2012 February 18