Above is an image of a Chandra Low Energy Transmission Grating (LETG) spectrum of a very bright X-ray source, the nova XTE J1118+480, showing only the shortest wavelengths. The major features are:

• Bright spot in center = the source (i.e., 0th order of the spectrum)
• Bright diagonal line extending corner to corner = the main dispersed spectrum (1st and higher orders)
• Bright line perpendicular to the main spectrum = cross-dispersion spectrum of 0th order, caused by the LETG fine-support structure
• Faint six-pointed star pattern in the center = diffraction of 0th order by the triangle-pattern coarse-support structure
• Faint fan of whiskers on either side = cross-dispersion orders caused by the fine-support structure. The main dispersed spectrum is 0th order of the cross-dispersion spectrum.

My primary job is to:

• Calibrate the intensities of the various LETG diffraction components shown above
• Calibrate the responses and efficiencies of the detectors (ACIS and HRC) used to record grating spectra
• Monitor detector changes over time and adjust operating parameters when necessary
• Develop methods to reduce detector background
• Assist LETG observers in setting up their observations.