OWLS

The Occultation Wave Limb Sounder (OWLS) is a NASA-sponsored mission launching aboard Momentus Vigoride 9 in 2027. Built at LASP, OWLS comprises two instruments: the Extreme Ultraviolet Occultation Photometers (EUV-OP) and the Compact Spectrograph for Occultations on Limb (CSOL). Together, they will address a critical gap in our understanding of how atmospheric gravity waves influence thermospheric temperature, enabling inference of key atmospheric properties — including temperature, density, and their variation with gravity wave energy and momentum flux.

Gravity waves (GWs) are atmospheric waves generated by disturbances in fluid motion, such as wind flowing over topography (e.g., mountain or lee waves) or deep atmospheric convection. They are of particular interest to the geospace community because they transport energy and momentum from the lower atmosphere into the upper atmosphere, potentially dissipating energy in the thermosphere at the altitudes where satellites orbit. Yet their net effect remains poorly constrained — it is still debated whether GWs produce a net heating or cooling of the thermosphere.

OWLS addresses this question through solar occultation measurements (see Figure 1), using the absorption of sunlight by atmospheric gases to infer thermospheric properties. CSOL (see Figure 2) characterizes GW activity in the lower and middle thermosphere, while EUV-OP measures temperature in the middle and upper thermosphere. Combined, these measurements allow the influence of GWs on thermospheric temperature to be directly observed for the first time.