Chandra at MPE

First Light from LETG!

On Sunday, September 6, 1999 the Low Energy Transmission Grating (LETG) on Chandra saw its First Light. $X-ray diffraction spectrum from Capella$ The 30,000 second image shows above the short wavelength part of the diffracted X-ray spectrum of the star Capella falling onto the central part of the channel plate detector, and below, the expanded wavelength range between 12 Å and 23 Å. More than 100 emission lines could be detected in the whole spectrum between 5 Å and 160 Å, with an up to now unprecedented resolving power of over 2000.

The LETG has been developed by the Max-Planck-Institut für extraterrestrische Physik (MPE) in Garching together with the Space Research Organization Netherlands (SRON) in Utrecht. It contains 540 individual diffraction gratings (1000 lines / mm), manufactured and aligned to a high degree of precision. The transmission grating positioned just behind the mirror system in the convergent beam disperses any incoming light into a (symmetric) spectrum to the left and right of the (nondispersed) zeroth diffraction order.