Abstract
The Bent Crystal Spectrometer (BCS) onboard the NASA Solar Maximum Mission was part of the X-ray Polychromator, which observed numerous flares and bright active regions from February to November 1980, when operation was suspended as a result of the failure of the spacecraft fine-pointing system. Observations resumed following the Space Shuttle SMM Repair Mission in April 1984 and continued until November 1989. BCS spectra have been widely used in the past to obtain temperatures, emission measures, and turbulent and bulk flows during flares, as well as element abundances. Instrumental details including calibration factors not previously published are given here, and the in-orbit performance of the BCS is evaluated. Some significant changes during the mission are described, and recommendations for future instrumentation are made. Using improved estimates for the instrument parameters and operational limits, it is now possible to obtain de-convolved calibrated spectra that show finer detail than before, providing the means for improved interpretation of the physics of the emitting plasmas. The results indicate how historical archived data can be re-used to obtain enhanced and new, scientifically valuable results.
Highlights
The diagnostic power and scientific value of high-resolution X-ray spectra emitted by hot (1 MK to ≈ 30 MK) astrophysical plasmas have been well established over the past half-50 Page 2 of 29 century
The entire dispersed spectrum can be registered with a position-sensitive detector, with the temporal resolution set by the encoding time of the detector and its electronics
We have described the instrumentation of the Solar Maximum Mission (SMM)/Bent Crystal Spectrometer in more detail than in previous publications
Summary
The diagnostic power and scientific value of high-resolution X-ray spectra emitted by hot (1 MK to ≈ 30 MK) astrophysical plasmas have been well established over the past half-. Until 1980, spacecraft-borne X-ray spectrometers used the conventional principle in which plane crystals diffract incoming X-rays according to the Bragg condition (see Equation (1) below). Rotating the crystals such that the angle of incidence varies with time generates a complete spectrum. The source variability is folded into the scanned spectrum, a considerable disadvantage during the flare’s impulsive stage for which the variability timescales are only a few seconds. This can be overcome with crystals that are slightly curved, such that the entire spectral range can be dispersed and instantaneously registered with a positionsensitive detector. We assess the instrument’s in-orbit performance including limits beyond which data become unreliable, some instrument calibration drifts and degradation, and changes revealed in images obtained by the Space Shuttle astronauts during the 1984 Repair Mission
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
