Seminars

Lecturer: Felix Friedl-Vallon (IMK-IFU)
Date: 2010-01-29 11:00
Place: Aniara

GLORIA-AB: An airborne Imaging FTS for atmospheric limb emission and nadir sounding

Felix Friedl-Vallon
Institut für Meteorologie und Klimaforschung
Karlsruhe Institute for Technology
Germany

Abstract
GLORIA-AB is an imaging FTS that will be flown on the German research aircraft HALO. The instrument allows observing the atmosphere in limb and nadir geometry. The scientific purpose in limb sounding mode focuses on dynamics, tropopause, TTL and polar UTLS imaging, in nadir mode biomass burning events and high precision methane measurements will be targeted.

The instrument is a joint development of the federal German research centres Jülich and Karlsruhe. Concept considerations for the instrument started in 2005 following a proposal for a space borne instrument to the German space agency DLR. The actual development of the airborne instrument started in 2006; a first flight shall be performed in 2010.

The heart of the instrument is a Michelson interferometer with a maximum optical path difference of ±10 cm. The atmospheric scene is imaged with an infrared lens system on the 256² element MCT focal plane array. In limb mode, a horizontal spatial coverage with a width of 18 km at the horizon and a sampling of 140 m is achieved. The vertical coverage extends from a tangent altitude of 4 km to +0.7° (all values given for a tangent altitude of 10 km and a flight altitude of 15 km).
The interferometer is suspended by a three axis gimballed frame system that allows to stabilise the scene on the focal plane array (FPA) by compensating the aircraft roll, nick, and yaw movements. In addition, in limb mode the horizontal viewing direction can be chosen freely in an angle range from 45° to nearly 135° to the flight direction. In nadir mode, the forward movement of the aircraft can be compensated for the duration of one interferogram. The necessary attitude information for the system is generated by a dedicated high precision inertial navigation system (INS) that is mounted on the azimuth frame of the system. The radiometric calibration system consists of two large area cavity blackbodies with very high emissivity and a thermoelectric temperature control that allows operating the blackbodies in the range from 15 K below to at least 30 K above ambient temperature. The instrument will operate autonomously on the aircraft. It will be mounted under the aircraft body in a dedicated belly bay at ambient pressure and temperature. To be able to react to unforeseen problems and to adapt the measurement plan, a low bandwidth satellite link to a supervising ground station will be implemented.

The presentation will focus on the design of the instrument and in particular of the spectrometer. Trade-offs and design decisions will be outlined. In addition, results of test and characterisation measurements will be discussed. Similarities and differences to the IRLS instrument on the proposed PREMIER satellite mission will be highlighted.

Created 2010-01-27 12:38:00 by Mats Holmström
Last changed 2010-01-27 13:28:05 by Mats Holmström