Monthly Newsletter

March 2001



Meetings
The Pegasus Rocket review will be held in Chandler, Arizona, April 3-4, 2001.

The SORCE Mission Operations Review will be held at LASP, Boulder, CO April 23-24, 2001.

SORCE is planning a Science Team Meeting July 9, 10, 11 2001 at the Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado.

SORCE scientists hope to present papers or attend the following summer 2001 meetings:

Workshop on the Evolving Sun and its Influence on Planetary Environments June 2001 Granada, Spain.

International Solar Cycle Studies 2001-Solar Variability, Climate and Spaceweather June 2001 Longmont, Colorado

IAGA Session on Solar Variability August 2001 Hanoi, Vietnam

SORCE March 2001 Project Summary
SORCE remains on schedule and within budget. No mission descopes are required at this time. Late delivery of key spacecraft components has resulted in build and testing schedule revision, and to date, there has been no unfixable impact to the program, but instrument integration slack has been depleted. Remanufacture of the spacecraft bench and late delivery of Alenia transceiver have impacted the spacecraft schedule. Additional testing facilities have been arranged at Ball Aerospace and additional test equipment has been purchased by LASP to facilitate project completion. A science support position has been offered as well. Dr. Doug Rabin (GSFC Division 682) has been appointed Deputy Project Scientist for SORCE. The SORCE ATBD will be resubmitted in March after revision and updating.

SORCE Mininum Science Criteria has been defined:

  • Achieve orbit and complete on-orbit check out for the SORCE spacecraft and instruments.

  • Capture and document daily values of Total

  • Solar Irradiance (TSI) and Spectral Solar Irradiance (SSI) for a duration of at least 18 months (>95% complete data record)

  • Produce calibrated and fully validated measurements of TSI with:
    • Absolute accuracy of 300 ppm (3s)

    • Precision and long-term relative accuracy
      of about 30 ppm/yr.

  • Produce the first spectral solar irradiance
    dataset covering the complete solar spectrum, 120 to 2000 nm (~95% of TSI), with:

    • Accurate determination of solar variablility

    • Spectral resolution and absolute accuracy suitable for use in Earth climate studies.

  • In conjunction with ESDIS, capture, archive and distribute to the scientific community the TSI and SSI data products.
TIM Shuttle Flight Science Objectives
  • Show that 100 ppm (1s) accuracy can be achieved with an instrument taken to space and returned for (re)characteriazation.

  • Direct comparison of TIM and SOLCON

  • Refine TIM characterization and operation procedures

TIM Status
TIM is 90% complete with a few areas of work remaining. Kinematic mounts, EMI filter brackets and adjustment and test of door mechanisms are mechanical areas of continued work, and additional grounding is required in the electrical area. Software learning curves have been overcome and progress is smooth. Improved performance has been achieved in the ability to change program parameters. There are diverse and ongoing housekeeping tasks to be done, but overall progress on TIM is excellent. First light was seen on March 29.

SIM Status
SIM is making rapid strides in flight build. SIM passed vacuum/pressure test. The vacuum test was stopped at pressure of 1.1x10-6 torr. RGA analysis showed most of the partial pressure was due to residual water vapor. SIM held 1.2 atmospheres for 72 hours. SIM focal plane detectors are assembled, tested and mounted in the flight case and alignment and focus are underway. The flight drives for the Fèry Prism drive have been assembled and characterized, and flight electronic boards are ready for fabrication. The prism drive operation and photodiodes are completely under DSP control, and lab spectra are being acquired. The mechanical fabrication of the calibrator system is complete, and assembly is underway. The flight beamsplitter has been delivered and the flight build of the periscope has begun. ESR characterization is 75% complete, but the SIM ESR DSP code still needs test. SIM slit width calibrations are complete, slit height is being analyzed and slit throughput calibrations are underway.

SOLSTICE Status
SOLSTICE is 90% complete. Instrument mechanical, optical, grating drive, and detector end-to-end testing is complete and instrument performance meets or exceeds requirements on the bench! A hardware fringe counter for the grating drive has been integrated into the DSP code and tested. The grating drive will now keep position after any external disturbance. Alignment stability tests are underway as well as preenvironmental test tasks. The cover/bench rework is complete but still must undergo test. Other loose ends such detector head noise quantitative assessment still must be pursued. The SOLSTICE A unit went to SURF on March 26, was successfully
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