Tangent height accuracy of superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on International Space Station (ISS)

The attitude detection system installed in the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) had insufficient angular precision for limb observation. While the SMILES observation provides extremely low-noise emission spectra, the large error in the tangent height of limb viewing due to the poor knowledge of the attitude often limits the accuracy of the SMILES products, such as volume mixing ratio of atmospheric molecules. The attitude data from a ring laser gyroscope (RLG) installed in a nearby experiment unit, Monitor of All-sky X-ray Image (MAXI), is used to improve the tangent-height error. We create a customized attitude data set from the RLG data initialized with information from the SMILES star sensor. Applying this customized RLG attitude, we can know the tangent height of limb observations with an improved precision of less than 140 m.