Since returning to science data collection on Jan. 27, 2013, after a 10-day precautionary wheel rest safe mode, the spacecraft has been performing well and continues to make science observations. The next monthly data download from the spacecraft is planned for March 6-7.
The team continues to monitor the health of the spacecraft and reaction wheel friction levels during semi-weekly contacts using NASA's Deep Space Network. Preliminary indications suggest that reaction wheel #4 continues to exhibit higher levels of friction after the wheel rest operation. During the March monthly download, high rate data of the wheel friction levels will be returned from the on-board recorder and the team will be able to perform a more thorough analysis.
Communications with Kepler during the semi-weekly contacts is accomplished using the spacecraft's low-gain antenna (LGA) that operates on an X-band frequency. Low-rate engineering data is brought down through the LGA while the spacecraft's orientation remains fixed on the target stars. The collection of science data is not interrupted for semi-weekly contacts. Once a month, a complete science and engineering data set is downloaded from the on-board solid-state recorder. During these monthly downloads, the spacecraft is turned away from its target stars to point the high-gain antenna (HGA) at Earth, temporarily interrupting the scientific observations. These downloads are thus able to return data at a much higher rate on a Ka-band frequency. The monthly downloads are typically done at a downlink rate of 4.3 Mbps, while the semi-weekly contacts can drop to data rates as low as 100 bps, depending on range and spacecraft orientation.
On Feb. 9-15, Kepler scientists joined astronomers from around the world for a conference about Exoplanets in Multi-body Systems in the Kepler Era, at the Aspen Center for Physics in Aspen, Colo. At the six-day gathering, scientists discussed the impact that the Kepler data on multi-planet systems have on current and future understanding of planet structure, the formation of planetary systems, their evolution over time, and the impact on the potential habitability of other worlds.
Last week the Kepler team announced the discovery of the smallest planet yet found around a star like our sun. Dubbed Kepler-37b, the planet is slightly larger than our moon, measuring about one-third the size of Earth, which made its detection a challenge. The research team used asteroseismology, the study of the interior of distant stars, to measure the radius of the host star Kepler-37 to three percent accuracy, which translates to exceptional accuracy in the planet's size. Kepler-37 is the smallest star where this technique has been used to precisely measure a star's size and, therefore the size of the planet.
March 6 is the fourth anniversary of the Kepler launch. Through the first 22 months of science operations, Kepler has cataloged 2,740 planets candidates and confirmed 114 as planets - and the count is expected to grow. Along its journey, Kepler has found planets and planetary systems that made astronomy firsts. These include: Kepler-10b, the first rocky planet outside our solar system; Kepler-11, an intriguing and tightly compacted six-planet system; Kepler-16b, the first double-star planet; Kepler-22b, Kepler's first habitable zone planet around a sun-like star; and the latest confirmation, Kepler-37b, a very small planet the size of Earth's moon. Kepler has also discovered eccentric binary stars, known as Kepler's "heart-beat stars" in very tight orbits resulting in tidally induced pulsations.
The first four years have been an amazing ride. We are sure that Kepler's best discoveries are yet to come.