continuously. Despite the adaptations of TES operators, the degradation got worse with time and in 2017 the instrument lost operations for approximately half the year. It will continue to receive enough power to keep it from getting too cold which could affect the two remaining functioning instruments. As of 2020, the expected constellation exit date is December 2023. An extended mission, below the A-train could push decommissioning back to late 2025 or as far as 2036. Predicted re-entry would be 2048. Instruments Aura carries four instruments for studies of atmospheric chemistry: HIRDLS — High Resolution Dynamics Limb Sounder — measures infrared radiation from ozone, water vapor, CFCs, methane and nitrogen compounds. Developed jointly with the United Kingdom Natural Environment Research Council. HIRDLS capabilities were compromised at launch when a piece of Kapton film in the instrument came loose and blocked much of the aperture, allowing only a partial view. The blockage prevented certain types of observations and necessitated the development of algorithms to remove the effects due to the blockage. This unanticipated algorithm developmental effort delayed data delivery. The HIRDLS chopper motor stalled on March 17, 2008, and HIRDLS has not produced science since. MLS — Microwave Limb Sounder — measures emissions from ozone, chlorine and other trace gases, and helps to clarify the role of water vapor in global warming. The MLS instrument package is divided into the THz, GHz, and spectrometer modules. The THz module was developed to measure the OH radical in the stratosphere and mesosphere using heterodyne detection of thermal emission. These modules observe emissions across 20 bands. In February 2006, band 13, the primary MLS band for measuring HCl, began to exhibit symptoms of aging and was deactivated to conserve life. It now only makes periodic observations. On August 6, 2013, band 12, which measures N2O, shut down. OMI — Ozone Monitoring Instrument — uses ultraviolet and visible radiation to produce daily high-resolution maps. Developed by the Finnish Meteorological Institute and the Netherlands Agency for Aerospace Programmes. In 2007, OMI began to experience a "row anomaly" which affected the quality of the radiance data. The row anomaly has continued to progress since then, with periods of stability. TES — Tropospheric Emission Spectrometer — measured tropospheric ozone in infrared wavelengths, also carbon monoxide, methane and nitrogen oxides. TES's laser A, which was used for retrieving interferometer control, began operating below peak in 2007 but was resurrected