MAESTRO (Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) is a small spectrophotometer designed and built in a partnership among the Meterological Service of Canada (MSC), the University of Toronto, and EMS Technologies in Ottawa. The 8-kg instrument was designed to cover the 285-1030 nm region in two overlapping segments. The use of two spectrographs (280-550 nm, 500-1030 nm) reduces the stray light and permits simultaneous measurements of the two bands with spectral resolution of 1-2 nm, depending on wavelength. The detectors are 1024 linear EG&G Reticon photodiode arrays.
The design is based on a simple concave grating with no moving parts. The entrance slit is held horizontal with respect to the horizon during sunrise. The ACE-FTS, imagers, and MAESTRO all share a single suntracker and have approximately the same direction of view. The MAESTRO SNR is in excess of 1000. While the ACE mission works primarily by solar occultation, MAESTRO is also able to make near-nadir solar backscatter measurements like the GOME instrument on the European ERS-2 satellite.