European Spacecraft Now Orbiting Venus

April 11, 2006 | The European Space Agency has extended its string of recent interplanetary successes by safely placing a spacecraft in orbit around Venus. Launched by a Russian Soyuz-Fregat rocket last November 9th, Venus Express fired its braking rocket early this morning for 50 minutes, long enough to slow its velocity by more than 1 kilometer per second. This maneuver placed the craft in a highly elongated, 9-day orbit around Venus that dips to within 400 km of the planet's surface. During the next four weeks ground controllers will tighten the trajectory to achieve a looping 24-hour polar orbit that ranges in altitude from 250 to 66,000 km. Modeled closely after the highly successful Mars Express craft now orbiting the Red Planet, Venus Express carries a suite of seven instruments. Its science team hopes to gather data for at least two full Venus years (486 days), focusing on the chemistry and dynamics of the planet's dense atmosphere, the nature of its opaque cloud layers, and the global electromagnetic environment.

More details about the mission are found at the Venus Express Web site.

Hubble View Downsizes "10th Planet"

April 12, 2006 | When the discovery of the giant Kuiper Belt object 2003 UB313 was announced last year, astronomers estimated its diameter to be roughly a third greater than that of Pluto. Subsequent infrared scrutiny by the Spitzer Space Telescope and a groundbased radio telescope seemingly confirmed that the object had a diameter near 3,000 kilometers (with an uncertainty of roughly 400 km). But Hubble Space Telescope images obtained last December barely resolved the object, and a careful analysis shows that it is likely 2,400 ± 100 km across — just 5% bigger than Pluto. According to Michael E. Brown (Caltech), who led both the discovery team and the recent Hubble effort, this means that 2003 UB313 has an extremely bright icy surface, one that reflects more than 85% of the sunlight that strikes it. (Saturn's moon Enceladus is the only solar-system object with a more reflective surface.) Right now 2003 UB313 is about 14½ billion km (9 billion miles) from the Sun, near the most distant — and coldest — point in its 560-year-long orbit. Brown's team theorizes that any nitrogen or methane in its atmosphere has precipitated onto the surface as a uniformly bright coating of frost. Moreover, the overly-large diameter derived from thermal-infrared studies suggests, in part, that the object might be oriented with one of its poles facing Earth.

Details about the new Hubble observations are here. Brown's Web site devoted to 2003 UB313 is here.

Japanese Space Observatory Nears "First Light"

April 13, 2006 | Officials of the Japan Aerospace Exploration Agency (JAXA) announced today that the aperture door to the Akari space observatory has been opened, paving the way for "first-light" images next month. Launched on February 21st from the Uchinoura Space Center on Kyushu Island, Akari circles Earth at an altitude of 745 kilometers in a Sun-synchronous polar orbit. The spacecraft is designed to conduct an all-sky survey over the broad infrared wavelength range of 1.7 to 180 microns. It's equipped with a three-channel camera for imaging specific targets at near-infrared wavelengths and a four-channel photometer to detect and map faint sources at longer wavelengths. The primary mirror of its supercooled optical system is 68.5 centimeters (27 inches) across, which should yield a more detailed and sensitive survey than that made by the Infrared Astronomical Satellite in 1983.

Formerly designated Astro-F, Akari is Japanese for "a light." To learn more about the mission, see the description on the JAXA Web site.

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