Here we report on the first successful exoplanet transit observation with the Stratospheric Observatory for Infrared Astronomy (SOFIA). We observed a single transit of the hot Jupiter HD 189733 b, obtaining two simultaneous primary transit lightcurves in the B and z ′ bands as a demonstration of SOFIA's capability to perform absolute transit photometry. We present a detailed description of our data reduction, in particular the correlation of photometric systematics with various in-flight parameters unique to the airborne observing environment. The derived transit depths at B and z ′ wavelengths confirm a previously reported slope in the optical transmission spectrum of HD 189733 b. Our results give new insights to the current discussion about the source of this Rayleigh scattering in the upper atmosphere and the question of fixed limb darkening coefficients in fitting routines.As an airborne observatory, SOFIA has a number of potential advantages for precise time-domain spectrophotometric observations of transiting exoplanets. Ground-based observations are significantly affected by variations of absorption from telluric gases, in particular H 2 O, in the Earth's atmosphere, and these same gases are also the species of interest in exoplanet atmospheres; SOFIA can observe in important atmospheric windows not observable from the ground (14; 15; 16; 17).These are mostly the water bands but also CO, CH 4 , CO 2 are much better mixed and therefore reduce the temporal variation in these bands, which is a crucial point for time-series observations.

We report observations of a stellar occultation by Pluto on 2019 July 17. A single-chord high-speed (time resolution = 2 s) photometry dataset was obtained with a CMOS camera mounted on the Tohoku University 60 cm telescope (Haleakala, Hawaii). The occultation light curve is satisfactorily fitted to an existing Pluto's atmospheric model. We find the lowest pressure value at a reference radius of r = 1215 km among those reported after 2012, indicating a possible rapid (approximately 21 +4−5 % of the previous value) pressure drop between 2016 (the latest reported estimate) and 2019. However, this drop is detected at a 2.4σ level only and still requires confirmation from future observations. If real, this trend is opposite to the monotonic increase of Pluto's atmospheric pressure reported by previous studies. The observed decrease trend is possibly caused by ongoing N 2 condensation processes in the Sputnik Planitia glacier associated with an orbitally driven decline of solar insolation, as predicted by previous theoretical models. However, the observed amplitude of the pressure decrease is larger than the model predictions.

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