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Overview of the ground and onboard calibration for Aspera SmallSat

Presentation #107.05 in the session Instrumentation for Space Missions.

Published onJul 01, 2023
Overview of the ground and onboard calibration for Aspera SmallSat

In this talk, we provide an overview of the ground and in-orbit calibration strategy for the Aspera SmallSat mission. Aspera is a NASA Astrophysics Pioneers mission dedicated to detecting and mapping the diffuse OVI emission from the warm-hot Circumgalactic Medium (CGM) of nearby galaxies. The payload for Aspera is a two-channel slit spectrograph that is optimized to measure the OVI emission line (1032 Å rest frame at R~1200) in the Far-Ultraviolet (FUV).

The two identical channels utilize a modified Rowland circle design with highly optimized FUV coatings on the primary mirrors and holographic gratings. They share a single cross-delay line microchannel plate (XLD-MCP) with high QE in the 1030-1040 Å bandpass for Aspera. Once built, the instrument will be calibrated in the vacuum with an FUV monochromator setup to measure the as-built spectral and spatial resolution and effective area. These measurements would benchmark the instrument performance and would be used for comparison with in-orbit performance and degradation.

In orbit Aspera will observe spectrophotometric standard white dwarfs previously observed and calibrated by the FUSE mission. The high resolution and high photometric accuracy observations of these targets from FUSE will be used for spectral and photometric calibration of Aspera. Astrometric calibration would be performed by slewing the slit across selected bright white draft targets to derive the in-flight pointing offsets between the instrument boresight and spacecraft pointing. The calibration operations will be repeated at periodic intervals to track for any degradation in instrument performance over its 8-month mission life.

This presentation will provide an overview of the ground calibration activities and in orbit observation plan and demonstrate how the calibration results would be applied to science data. We will briefly discuss the challenges and the solution we have developed for testing and calibrating this highly contamination-sensitive UV instrument.

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