On Sunday, September 6, 1999 the Low Energy Transmission Grating (LETG)
on Chandra saw its First Light.
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.