Venus Express Update
The European Space Agency has released its periodic report on the research being conducted the Venus Express orbiter. This one includes the end of the twenty-third eclipse season, end of the fourteenth Earth occultation season and continuation of the surface imaging campaign.
SCIENTIFIC FOCUS
This reporting period falls under the 89th Medium Term Plan (MTP), which covered the period from 3 February to 2 March 2013. The fourteenth radio occultation season ended on 16 February, and the twenty-third eclipse season ended on 23 February.
This MTP was ‘hot’, meaning that nadir observations, if carried out, would expose thermally sensitive faces of the spacecraft to solar illumination, limiting observation times. The data rate during this period was very low, as the Earth-Venus separation approaches the orbital maximum during March 2013. Local time at ascending node (LTAN) changed from 11:45 hrs to 14:45 hrs, which meant that the observations were carried out during ‘terminator orbits’.
The Venus-Earth-spacecraft geometry was such that all Earth occultations and solar eclipses occurred simultaneously, after orbit pericentre. Hence, radio science occultation measurements and spectrographic eclipse observations were alternated during close approaches to the planet. Both types of observations were performed to obtain thermal sounding measurements – these provide thermal profile data for the upper and middle altitudes of the atmosphere and allow scientists to study the atmospheric temperatures between altitudes of roughly 50 to 100 km. The sounding measurements were obtained during eclipse entry and exit with the Solar Occultation at Infrared (SOIR) channel of the SPICAV (Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus) instrument. Earth occultation data (acquired during Earth occultation entry and exit) were obtained using the VeRa radio science experiment.
The surface mapping campaign, begun during the previous planning period, continued in this one. Observations of the surface during the eclipse continued in at least half the orbits until the eclipse duration dropped below 25 minutes (on 16 February).
The campaign was conducted using the Venus Monitoring Camera. Heat given off by the planet’s surface can be seen from orbit via one small ‘window’, (infrared emission at 1 micron that can penetrate the clouds) using one of the filters of the VMC tuned to this frequency. The emission is, however, somewhat distorted on its path through the clouds, so the VMC can only obtain low-resolution infrared observations of the surface of Venus, and only under complete eclipse conditions. The imaged surface targets include:
Ishtar Terra, (55° – 75°N, 310° – 60°E)
Bell Regio area (e.g. Tepev Mons), (27° – 37°N, 44° – 52°E)
E. Eistla Regio (10° – 20°N, 36° – 52°E)
Bereghinia Planitia (28°E, 39°N)
Oshun Farra (4.2°N, 9.3°N)
Dzalarhons Mons (0.5°N, 34°E)
Un-named Tessera (4°S – 4°N, 36° – 46°E).
