Overview and Status of the SORCE

Transcription

1 Overview and Status of the SORCE Laboratory for Atmospheric and Space Physics, University of Colorado (303) July 17,

2 July 17,

3 The Earth's Radiation and Energy Balance July 17,

4 Endorsement(s) SOLAR INFLUENCES ON GLOBAL CHANGE (1994 NATIONAL ACADEMY OF SCIENCES REPORT) Primary Recommendation: One activity ranks above all others for determining solar influences on global change: Monitor the total and spectral solar irradiance from an uninterrupted series of spacecraft radiometers employing in-flight sensitivity tracking. July 17,

5 Basic Radiometic Quantities The total irradiance or radiant f lux density is the radiant flux across a surface element, da : E= dφ da {W / m 2 } dφ da The spectral irradiance, E λ, is the radiant flux density per unit wavelength interval: E λ = d2 Φ dadλ {W / m 3 } [1368 W/m 2 ] NOTE: the Total Solar Irradiance, TSI, is the integral over all wavelengths o f the Solar Spectral Irradiance. E= E λ dλ λ=0 July 17,

6 SORCE Science Objectives Establish a data set of Total Solar Irradiance (TSI) 5-year duration from December 2002 to November 2007 Daily measurements with an absolute accuracy better than 300 ppm (3σ) Relative accuracy between measurements of 0.001% (10 ppm) per year Establish a data set of Solar Spectral Irradiance 5-year duration from December 2002 to November 2007 Spectral coverage from 1 nm to 2 µm Daily measurements with an absolute accuracy of 2 to 5% in the ultraviolet, and 0.1 % in the visible to near infrared Improve our understanding and generate new inquiry How does a variable solar irradiance affect our atmosphere and climate? How and why does variability occur at the Sun? use this knowledge to estimate past and future solar activity combined standard uncertainty July 17,

7 SORCE Spectral Coverage July 17,

8 Why the Solar Irradiance Varies Changes in distance to the Sun 27-day rotation period coupled with a non-uniform distribution of brightness Intrinsic changes in the Sun magnetic activity, radius, luminosity, temperature, flares, etc. Periodicities to Consider: 1 year year year year Orbital 100 Kyear 400 Kyear 27 day 11 year 22 year Solar 88 year 208 year July 17,

9 Current Record of TSI Measurements July 17,

10 Concept of Electrical Substitution Radiometers Based on the measurement of heat flux. Two identical sensors, one active and the other used as a reference, are connected so that they are in the same environment and at the same temperature. Joule heat is supplied to each sensor by an actively controlled heater circuit. These sensors have high absorptance in order to efficiently collect radiation. Photon energy is completely converted to heat. A shutter opens and solar radiation is allowed to fall on the active sensor a corresponding amount of Joule heat must therefore be removed from the active sensor in order to maintain the heat flux balance. The change of Joule heat to the active sensor is equivalent to the amount of radiation now incident upon it. July 17,

11 Total Irradiance Monitor TIM Mass of 6.5 kg 13 x 13 x 26 cm 3 For redundancy there are two pairs of cones either can be the active sensor, and each cone has its independent shutter Cones have a single point thermal ground They are thermally and mechanically mounted at their centers of gravity by stainless steel spiders Heaters and thermistors are terminated at diamond standoffs these thermal shunts precisely define nodes for characterization July 17,

12 Spectral Irradiance Monitor SIM 50 k? thermistors 100 k? thin film resistor July 17,

13 SOLSTICE SOlar Stellar Irradiance Comparison Experiment July 17,

14 XPS XUV Photometer System July 17,

15 How SORCE Has Evolved NASA AO-88-OSSA-1 EOS SOLSTICE selected February 1989 Science Objectives: Make daily measurements of solar spectral irradiance between 1 nm and 2000 nm, achieve state-of-the-art precision and accuracy Continue the data base of solar ultraviolet irradiance (120 < λ < 300 nm) first established by the UARS SOLSTICE (1991 to present) NASA AO-97-MTPE-01 for TSIM selected February 1999 Science Objectives: Extend the monitoring of Total Solar Irradiance (TSI) beyond that of EOS/ACRIM, at or exceeding the absolute accuracy of 1000 ppm Spectral Irradiance measurements from 200 nm to 2 µm Combined Mission Letter of April 1999 from Ghassem Asrar, NASA Associate Administrator For Earth Science... new programmatic direction is being provided to combine the SOLSTICE/SAVE and TSIM missions. The new combined mission will be called the Solar Radiation and Climate Experiment (SORCE). July 17,

16 Overview of the LASP Approach to SORCE LASP manages the entire SORCE program including: LASP has built and delivered four instruments 1 TIM the Total Irradiance Monitor - Measures TSI - A new development that incorporates the modern, state-of-the-art technologies of the Electrical Substitution Radiometer (ESR) - It takes full advantage of the best heritage of previous radiometers 2 SIM the Spectral Irradiance Monitor - Measures spectral irradiance 200 nm to 2000 nm - A new development using prism as the dispersing element - Also using an ESR (miniaturized) 3 SOLSTICE the Solar Stellar Irradiance Comparison Experiment - Measures spectral irradiance 120 to 320 nm - An evolution and refinement of our UARS SOLSTICE - Observes bright, blue stars as a long term calibration standard 4 XPS XUV Photometer System - Measures broadband spectral irradiance 1 to 30 nm - An instrument of identical design to the XPS operates on the TIMED Program July 17,

17 LASP Approach to SORCE (cont.) has provide a highly capable, and low-risk spacecraft We will launch SORCE in November 2002 on a Pegasus XL We will operate the SORCE for a period of five years We will process, analyze, validate and distribute all irradiance data July 17,

18 Key SORCE Personnel (It takes a village to launch SORCE) (LASP) Tom Sparn (LASP) Tom Woods (LASP) George Lawrence (LASP) Jerry Harder (LASP) Greg Kopp (LASP) Bill McClintock (LASP) Rick Kohnert (LASP) Mike Anfinson (LASP) Tim Holden (LASP) Bill Ochs (GSFC) Debbie Dodson (GSFC) Bob Cahalan (GSFC) Doug Rabin (GSFC) Don Anderson (NASA HQ) Principal Investigator Program Manager Project Scientist Instrument Scientist Instrument Scientist Instrument Scientist Instrument Scientist System Engineer Instrument Manager Spacecraft Manager SORCE Project Manager Resource Manager Project Scientist Deputy Project Scientist Program Scientist Additional Co-Investigators: Dominique Crommelynck Peter Fox Claus Fröhlich Judith Lean Julie London Peter Pilewskie Ray Roble Paul Simon Dick White SORCE Co-Investigator July 17,

19 Shipment to Orbital Dulles Facility July 17,

20 Instrument Module at Orbital July 17,

21 Testing at Orbital EMI/EMC Solar Array Deployment July 17,

22 SORCE (Launch November, 2002) SORCE motor at WTR in December 2001 HESSI at KSC July 17,

23 The Future UARS will more than likely end in October of this year ACRIMSAT, SOHO, and ERBS will likely continue (?) SORCE will launch in November and has a goal to operate until 2007 NPOESS will carry TIM and SIM instruments beginning in 2012 There will likely be a 5 year gap between SORCE and NPOESS NASA intends to fill the GAP with the SIGF Mission, but there are no $ s in 2003 for a new start Remember: Primary Recommendation: One activity ranks above all others for determining solar influences on global change: Monitor the total and spectral solar irradiance from an uninterrupted series of spacecraft radiometers employing in-flight sensitivity tracking. This message keeps getting lost Solar Irradiance Gap Filler July 17,