Monthly Newsletter

April 2003



Mission Update –
It has been three months since SORCE was launched! SORCE continues to make excellent daily solar and stellar observations, and the solar data are received two times each day. The biggest challenge currently is the task of verifying the four instruments calibrations and data processing software, so the measurements are truly valid and ready for the science community.

Instrument Status –
The calibration process continues on all of the SORCE instruments, which are currently operating in normal mode. The preliminary data products generated are meticulously reviewed, and compared to earlier instrument expectations. The data are also compared with observations of similar instruments on other spacecrafts currently operating. After investigating the similarities and anomalies, scientists work towards data validation by improving data processing code.
As expected, each instrument is experiencing its own unique set of anomalies that requires further research. One step at a time, the instruments and data products are being fine-tuned to maturity, where the end result will be an accurate set of solar measurements.

A Closer Look at the XPS Instrument –
This newsletter explores the preliminary data results from the XPS (XUV Photometer System) instruments. The XPS measures the solar soft X-ray (XUV) irradiance from 1 to 34 nm and the bright hydrogen emission at Lyman-a (121.6 nm). The solar XUV radiation is emitted from the hot, highly-variable corona on the Sun, and these high-energy photons are a primary energy source for heating and


ionizing Earth’s upper atmosphere. The following images and captions were submitted by Tom Woods, XPS Instrument Scientist.

Time series of XUV radiation through the onset of solar cycle 23. Images at the top are obtained in bright helium emission at 30.4 nm by the SOHO EIT. These images indicate how different the Sun looks and behaves in the XUV compared to the visible. Sunspots, which are dark in the visible, are associated with strong magnetic fields that appear bright in the corona. Data shown here are from different wavelength bands, but scaled to SNOE 2-7 nm data. THE SORCE XPS measurements will continue this time series into the declining phase of the current solar cycle.

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