The Double Arm Linkage precision Linear motion (DALL) carriage has been developed as a simplified, rugged, high performance linear motion stage. Initially conceived as a moving mirror stage for the moving mirror of a Fourier Transform Spectrometer (FTS), it is applicable to any system requiring high performance linear motion. It is based on rigid double arm linkages connecting a base to a moving carriage through flexures. It is a monolithic design. The system is fabricated from one piece of material including the flexural elements, using high precision machining. The monolithic design has many advantages. There are no joints to slip or creep and there are no CTE (coefficient of thermal expansion) issues. This provides a stable, robust design, both mechanically and thermally and is expected to provide a wide operating temperature range, including cryogenic temperatures, and high tolerance to vibration and shock. Furthermore, it provides simplicity and ease of implementation, as there is no assembly or alignment of the mechanism. It comes out of the machining operation aligned and there are no adjustments. A prototype has been fabricated and tested, showing superb shear performance and very promising tilt performance. This makes it applicable to both corner cube and flat mirror FTS systems respectively.
The FIRST (Far-InfraRed Spectroscopy of the Troposphere) instrument is a 10 to 100 micron spectrometer with 0.64
micron resolution designed to measure the complete mid and far-infrared radiance of the Earth's Atmosphere. FIRST
has been successfully used to obtain high-quality atmospheric radiance data from the ground and from a high-altitude
balloon. A Fourier transform interferometer is used to provide the spectral resolution and two on-board blackbodies are
used for calibration. This paper discusses the recent re-calibration of FIRST at Space Dynamics Laboratory for absolute
radiance accuracy. The calibration used the LWRICS (Long Wave Infrared Calibration Source) blackbody, which NIST
testing shows to be accurate to the ~100 mK level in brightness temperature. There are several challenges to calibrating
FIRST, including the large dynamic range, out of phase light, and drift in the interferogram phase. The accuracy goal
for FIRST was 0.2 K over most of the 10 to 100 micron range, and results show FIRST meets this goal for a range of
target temperatures.
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