Mission Manager Update: K2 continues to shine
It’s been nine months since my last report, so what has the mission been up to?
Well, the search of the Kepler data has continued and is now in the home stretch. Last July we announced Kepler-452b, an older, larger planet than Earth, but one that orbits a star very much like our sun and has spent billions of years in its habitable zone. Kepler-452b joins the very interesting and growing group of near-Earth-size exoplanets – planets that orbit other suns – that are less than twice the size of Earth and reside in their sun’s habitable zone which is the distance from the star where liquid water might pool on the surface.
Also in July, we released our second-to-last exoplanet catalog, increasing the total number of candidates to more than 4,600, and added 12 small potentially rocky candidates in the habitable zone. This penultimate catalog was also noteworthy for being our first fully automated catalog, turning over the task of vetting potential exoplanets to software. Because it is so much faster, it means that for the first time, we were able to go back and reassess all the data from the mission, and to do so uniformly. And now we’re on the last lap, doing our final evaluation of the data to deliver the final mission catalog, which is anticipated early next year. Of course, the list of exoplanets will continue to grow as other observers and other missions take the baton and continue to expand the frontier.
To that end, our new K2 mission has been a smashing success! The spacecraft has operated beautifully, with scarcely a whiff of trouble. As part of our K2 mission strategy, we’ve relaxed the fault or sensitivity limits and taken on a bit more risk so that we wouldn’t have to interrupt the observing to correct minor issues. In response, the spacecraft appears to have rewarded our trust by operating more smoothly than it has at any other time in its history. As a result, the ground crew has had time to look for additional improvements. Since we began the K2 mission, we have improved the pointing, increased the duration of observations and increased the number of targets observed – all while spending less fuel than we expected. We now project that the spacecraft may have enough fuel to operate for nearly another three years!
Now we are preparing to embark on a new experiment, turning the spacecraft around and pointing the telescope in the forward velocity vector, where, instead of looking towards where it’s been, it will look in the direction of where it’s going. This special maneuver has the detriment of letting the Earth move through its field of view and putting a lot of light into the telescope, but it will let us look near the central bulge of our galaxy while ground-based observatories do the same thing, at the same instant. This unique coordinated observing lets astronomers look for exoplanets and other dark bodies by taking advantage of their ability to act as a gravitational lens, focusing the light of a background star and temporarily causing that star to brighten. This approach has been successfully used to detect exoplanets from the ground, but doing it simultaneously from the ground and a spacecraft fifty million miles from Earth will allow astronomers to determine the distance to these bodies using parallax – the effect whereby the position or direction of an object appears to differ when viewed from a different position. Calculations around this process can reveal the mass of found exoplanets. This special microlensing observing period or campaign will begin in April and end in July. During this time telescopes around the world will focus on a specific patch of sky in a joint effort to demonstrate the power of this technique, which will also be used by NASA’s Wide Field Infrared Survey Telescope, or WFIRST mission, planned to launch in the mid-2020s.
Meanwhile, the K2 mission, with its superb photometry applied to the ecliptic – the orbital path traveled around the sun by the planets of our solar system and the location of the zodiac – is opening the door to new scientific discoveries. In November, the Las Cumbres Observatory Global Telescope Network hosted a K2 science conference attended by nearly 200 scientists from around the world. Presentations described the science being conducted with K2 data from exoplanets to stellar physics to supernovae and black holes. We are seeing an explosion of scientific interest in the K2 mission, with a new generation of researchers coming to the forefront. Already K2 is starting to make a significant contribution to the number of exoplanets known, and is finding them closer to home than those discovered by Kepler, and around brighter stars that provide enough light to make them candidates for probing their atmospheres. The promise of the mission is extensive.
With the fuel savings achieved, the K2 mission has been invited to propose for a mission extension through the process of NASA’s astrophysics division’s senior review of operating missions.
To give a sense of the improvements that have been made since the start of the K2 mission, consider that we initially hoped to observe 10,000 target stars in each campaign, and we are now averaging nearly 30,000. And that we have balanced the spacecraft against the solar pressure so well that we can see a change in it’s pointing when transmitting data from its back-up antenna. Just think about that for a moment. This spacecraft, as big and heavy as an SUV, turns slightly just because we change the broadcasting antenna! This is like having your car begin to turn because of the blinking of your turn signal!
Finally, since my last report, we marked the retirement of the Kepler principal investigator, William Borucki, for whom we have so much to thank, and celebrated the 20th anniversary of the discovery of the first exoplanet. We have come a long way in the last 20 years, and with Kepler’s success we are riding the K2 mission into new territory.
