Venus Express radio occultation observed by PRIDE

¹ Joint Institute for VLBI ERIC, PO Box 2, 7990 AA Dwingeloo, The Netherlands
e-mail: bocanegra@jive.eu
² Department of Astrodynamics and Space Missions, Delft University of Technology, 2629 HS Delft, The Netherlands
³ Shanghai Astronomical Observatory, 80 Nandan Road, Shanghai 200030, PR China
⁴ University of Tasmania, Private Bag 37, Hobart, Tasmania 7001, Australia
⁵ Netherlands Institute for Radio Astronomy, PO Box 2, 7990 AA Dwingeloo, The Netherlands
⁶ California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125, USA
⁷ ACRI-ST, 260 route du Pin Montard, 06904 Sophia-Antipolis Cedex, France
⁸ Space Science and Engineering Center, University of Wisconsin, Madison, WI, USA
⁹ Xinjiang Astronomical Observatory, CAS, 150 Science 1-Street, Urumqi, Xinjiang 830011, PR China
¹⁰ NICT Kashima Space Technology Center, 893-1, Kashima, Ibaraki 314-8501, Japan
¹¹ Institute of Applied Astronomy of Russian Academy of Sciences, 191187 St. Petersburg, Russia

Received: 4 April 2018
Accepted: 14 February 2019

Abstract

Context. Radio occultation is a technique used to study planetary atmospheres by means of the refraction and absorption of a spacecraft carrier signal through the atmosphere of the celestial body of interest, as detected from a ground station on Earth. This technique is usually employed by the deep space tracking and communication facilities (e.g., NASA’s Deep Space Network (DSN), ESA’s Estrack).

Aims. We want to characterize the capabilities of the Planetary Radio Interferometry and Doppler Experiment (PRIDE) technique for radio occultation experiments, using radio telescopes equipped with Very Long Baseline Interferometry (VLBI) instrumentation.

Methods. We conducted a test with ESA’s Venus Express (VEX), to evaluate the performance of the PRIDE technique for this particular application. We explain in detail the data processing pipeline of radio occultation experiments with PRIDE, based on the collection of so-called open-loop Doppler data with VLBI stations, and perform an error propagation analysis of the technique.

Results. With the VEX test case and the corresponding error analysis, we have demonstrated that the PRIDE setup and processing pipeline is suited for radio occultation experiments of planetary bodies. The noise budget of the open-loop Doppler data collected with PRIDE indicated that the uncertainties in the derived density and temperature profiles remain within the range of uncertainties reported in previous Venus’ studies. Open-loop Doppler data can probe deeper layers of thick atmospheres, such as that of Venus, when compared to closed-loop Doppler data. Furthermore, PRIDE through the VLBI networks around the world, provides a wide coverage and range of large antenna dishes, that can be used for this type of experiments.