Universität zu Köln

Hinson, D. P., Linscott, I. R., Young, L. A., Tyler, G. L., Stern, S. A., Beyer, R. A., Bird, M. K., Ennico, K., Gladstone, G. R., Olkin, C. B., Paetzold, M., Schenk, P. M., Strobel, D. F., Summers, M. E., Weaver, H. A. and Woods, W. W. (2017). Radio occultation measurements of Pluto's neutral atmosphere with New Horizons. Icarus, 290. S. 96 - 112. SAN DIEGO: ACADEMIC PRESS INC ELSEVIER SCIENCE. ISSN 1090-2643

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Abstract

On 14 July 2015 New Horizons performed a radio occultation (RO) that sounded Pluto's atmosphere down to the surface. The sensitivity of the measurements was enhanced by a unique configuration of ground equipment and spacecraft instrumentation. Signals were transmitted simultaneously by four antennas of the NASA Deep Space Network, each radiating 20 kW at a wavelength of 4.2 cm. The polarization was right circular for one pair of signals and left circular for the other pair. New Horizons received the four signals and separated them by polarization for processing by two independent receivers, each referenced to a different ultra-stable oscillator. The two data streams were digitized, filtered, and stored on the spacecraft for later transmission to Earth. The results reported here are the first to utilize the complete set of observations. We calibrated each signal to remove effects not associated with Pluto's atmosphere, including the limb diffraction pattern. We then applied a specialized method of analysis to retrieve profiles of number density, pressure, and temperature from the combined phase measurements. Occultation entry sounded the atmosphere at sunset at 193.5 E, 17.0 S on the southeast margin of an ice-filled basin known informally as Sputnik Planitia (SP); occultation exit occurred at sunrise at 15.7 E, 15.1 degrees N - near the center of the Charon-facing hemisphere. Above 1215 km radius (similar to 25 km altitude) there is no discernible difference between the measurements at entry and exit, and the RO profiles are consistent with results derived from ground-based stellar occultation measurements. At lower altitudes the RO measurements reveal horizontal variations in atmospheric structure that had not been observed previously, and they are the first to reach the ground. The entry profile has a strong temperature inversion that ends 3.5 km above the surface, and the temperature in the cold boundary layer beneath the inversion is nearly constant, 38.9 +/- 2.1 K, and close to the saturation temperature of N-2. The exit profile has a much weaker inversion that extends all the way to the ground, where the air temperature is 51.6 +/- 3.8 K. Three factors appear to be responsible for the presence of a cold boundary layer in the entry profile (Forget et al., 2017): a substantial diurnal cycle of sublimation and condensation of N-2 ice in SP, the local time of the RO observation, and confinement within SP by the surrounding topography and katabatic winds. We have also determined the surface pressure and the local radius at both entry and exit. The best pressure reference is the mean value: 11.5 +/- 0.7 microbar at 1189.9 +/- 0.2 km. (C) 2017 Elsevier Inc. All rights reserved.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Hinson, D. P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Linscott, I. R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Young, L. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Tyler, G. L. UNSPECIFIED UNSPECIFIED UNSPECIFIED Stern, S. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Beyer, R. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bird, M. K. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ennico, K. UNSPECIFIED UNSPECIFIED UNSPECIFIED Gladstone, G. R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Olkin, C. B. UNSPECIFIED UNSPECIFIED UNSPECIFIED Paetzold, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schenk, P. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Strobel, D. F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Summers, M. E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Weaver, H. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Woods, W. W. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-227127
DOI:	10.1016/j.icarus.2017.02.031
Journal or Publication Title:	Icarus
Volume:	290
Page Range:	S. 96 - 112
Date:	2017
Publisher:	ACADEMIC PRESS INC ELSEVIER SCIENCE
Place of Publication:	SAN DIEGO
ISSN:	1090-2643
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language STELLAR OCCULTATIONS; SCIENCE OBSERVATIONS; JUPITERS IONOSPHERE; CONVECTION; SPACECRAFT; RESOLUTION; NITROGEN; METHANE; MISSION; IMAGER Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/22712