6. Chandra X-ray Observatory Report
Roger Brissenden (SAO) and Martin C. Weisskopf (MSFC)

Chandra has now carried out over 13 years of highly successful science operations. Chandra's overall observing efficiency has risen to the highest level of the mission, due to the evolution of Chandra's orbit, which has reduced the unproductive time spent in Earth's radiation belts. For the previous, current, and next observing cycle this has led to an substantial increase in the amount of observing time available. Science data processing, archiving, and distribution proceeds smoothly, with average time from observation to data delivery to observers remaining at about a day.

In response to NASA's request for proposals for the 2012 Senior Review of operating missions, the Chandra X-ray Center (CXC) submitted its proposal, prepared by CXC and Marshall Space Flight Center program staff, in January and made a presentation to the Senior Review committee in February. The committee's report rated the Chandra X-ray Observatory highly and described Chandra as one of the "two most important missions in this Senior Review." The committee recommended extending Chandra operations through 2016 and augmentation of the budget to restore planned cuts in the General Observer grants program.

In July, NASA extended the activities of the Chandra X-ray Center through September 2016 by exercising the first of two contract options. (The second option, which comes into play in 2015, would extend activities through September 2019.)

In December 2011, after several years of development and testing, new on-board software and ground-based procedures were implemented that enable one to command Chandra spacecraft maneuvers at the same time as the science instruments are stowed to protect them from solar and radiation-belt particles. This "split" commanding enables us to adapt to increasingly stringent operational constraints and heightened solar activity. It also increases spacecraft safety margins and in many cases speeds up the return to observing after periods of solar activity, further maximizing available observing time.

In May Chandra experienced a benign safemode, one of very few throughout the mission that was caused by a small change in the performance of the active Fine Sun Sensor (FSS) near the edge of its field of view. Recovery from the safemode was smooth and rapid, aided significantly by the split command load capability. We have mitigated future occurrences of the FSS effect by reducing the field of view.

The Cycle 14 Chandra peer review, held in June, approved 185 proposals, out of 672 submitted by researchers worldwide who requested 123 Msec of observing time, ~5.2 times greater than the time available. Among the approved proposals are four X-ray Visionary Projects (XVPs), which were allocated a total of 6 Msec. XVPs are longer observing programs intended to address major questions in astrophysics and to produce data sets of lasting value.

The Chandra X-ray Center conducted the workshop "X-ray Binaries, 50 Years Since the Discovery of Sco X-1" in July.

The Chandra Press Office issued 18 image releases and 10 science press releases, as well as a NASA media teleconference and an AAS press event. A complete listing is available at http://Chandra.harvard.edu/press.

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