The SOFIA Science Instruments

The SOFIA observatory had a wide range of scientific instruments (SI) at its disposal, which were typically installed on the telescope's instrument flange for two to three weeks at a time. This allowed spectroscopic, photometric, and polarimetric measurements to be carried out. The scientific observations determined which of the instruments had to be used. The flight planners' task was to combine different observations with the same instrument at the right time of year. This is because not every astronomical object is visible throughout the year; some can only be seen from the northern or southern hemisphere of the Earth.
The FPI+ (Focal Plane Imager) tracking camera occupies a special position among the instruments. It used the telescope optics and was able to perform photometry with high temporal resolution during the observation of stellar occultations. In addition, it was used as a telescope guide camera for all observations.
The telescope also had two additional cameras, the Wide Field Imager (WFI, focal length 136 mm, field of view 6 x 6 degrees) and the Fine Field Imager (FFI, focal length 733 mm, field of view 67 x 67 arcmin). These were attached to the front ring of the telescope and were primarily used for orientation in the sky and for recognizing star patterns by the telescope operators. WFI and FFI are not classified as scientific instruments.

The most important scientific instruments used by SOFIA, whose data is also being processed as part of the SDC project, were (in alphabetical order):

High-resolution Echelon/Echelle spectrograph for mid-infrared (4.5–28.3 mm) and high spectral resolution up to R~105.

Imaging grating spectrometer with two channels in the far-infrared wavelength range (51–120 mm, 115–200 mm) and medium resolution of R~600–2,000).

Dual-channel camera in the mid-infrared range (5–40 mm), which also enabled low-resolution spectroscopy (R~600).

Guide camera of the telescope, photometric scientific instrument, primarily used for stellar occultations and as an analysis instrument for monitoring the observatory's performance.

Heterodyne receiver, which enabled extremely high-resolution spectroscopy (R~108) in different frequency bands of the far-infrared spectrum in two different configurations.

Dual-channel far-infrared camera with broadband filters that are sensitive in the wavelength range between 50 and 240 mm and can also measure polarization. This made it possible to measure and visualize magnetic fields in space.