Thanksgiving Prep: Preheat At 90 For 15 Minutes

John Scott is a mission planner for Chandra’s Flight Operation Team, and from time to time provides an inside look for the outside world on just how people take care of this remarkable spacecraft. This entry has a bit of a mystery in the second half of the title. If you have a guess to what it means to "Preheat at 90 for 15 minutes," then post it to the comment section. (Note to the rest of the Flight Ops Team: you're not eligible!) If someone comes up with the right answer – or close to it – we’ll send you a Chandra poster.

As most of the nation will spend the Thanksgiving holiday devouring a stuffed turkey in the warmth of their dining room, the Chandra X-ray Observatory will give thanks for the three batteries that will keep it powered during the first day of its 22nd eclipse season. With only three and a half weeks of eclipses (eight eclipses total), this season will be brief when compared to the upcoming eclipse seasons in the following few years.

The observatory experiences two eclipse seasons per year in which the Earth blocks the Sun and its potent solar energy from Chandra's six solar arrays. While the spacecraft is fully prepared for this upcoming eclipse season, it took the effort of an entire team to make it so. Chandra's Flight Operations Team, located in Cambridge, Massachusetts, spends many hours on analysis and preparing the spacecraft for its cold trip through the sunless sky.



It all begins with the team's Electrical Power Subsystem engineer. He spends the few months leading up to the eclipse season using advanced tools to predict the length of each eclipse, determining whether the eclipse will require additional, commanded-on equipment, and preparing procedures for the spacecraft operators in case of an eclipse emergency. Simultaneously, the team's Deep Space Network (DSN) schedulers negotiate specific communications time on any of the six available JPL stations so that the team’s spacecraft operators can watch the live telemetry as the spacecraft traverses through the eclipse. In the weeks leading up to each eclipse, the team's Mission Planners configure the daily loads (a time-based series of commands that drive the spacecraft in its daily operations) to position Chandra's telescope and solar array axes normal to the sun-line and include commanding to configure the spacecraft for the eclipse. A day prior to the first eclipse, the spacecraft operators perform commanding to enable onboard contingency protection that will execute preapproved commands in the case of an emergency, even if the team is not in communication with the spacecraft. Two days prior to each eclipse, the onboard daily loads set timers that tell the onboard computer the duration of each eclipse.



As with a great Thanksgiving dinner, it's all in the prep work. When the eclipses actually arrive, the team watches the spacecraft go into and come out of each eclipse, ensuring its safety. Given the preparation that goes into each eclipse season, the onboard emergency protection, and the eyes of our trained operators, the spacecraft, though without sunlight, is in good hands. Shortly following the final eclipse of the season, the spacecraft is reconfigured for nominal operations and the EPS engineer begins to analyze the eclipse data in more detail, preparing for the next, lengthy eclipse season, which will occur in the spring of 2010.

While I'm sure the spacecraft would much prefer to be kicked back in a recliner, enjoying the warmth of a fire, half-watching the holiday game in a tryptophan-induced coma, it will instead traverse through the first eclipse of its fall season, in a dutiful effort to bring us the best x-ray data imaginable.

-John Scott

To read this and other official Chandra blogs click here:
http://chandra.harvard.edu/blog/node/173

Crab Nebula: The Crab Nebula: A Cosmic Icon


For more information and images click here:
http://chandra.harvard.edu/photo/2009/crab/

NASA's Great Observatories Examine the Galactic Center Region


Credit:X-ray: NASA/CXC/UMass/D. Wang et al.; Optical: NASA/ESA/STScI/D.Wang et al.; IR: NASA/JPL-Caltech/SSC/S.Stolovy

• A new image of the center of the Milky Way combines data from NASA's three Great Observatories.

• In this image, X-rays from Chandra are blue and violet, near-infrared emission from Hubble is yellow, and Spitzer's infrared data are red.

• Large prints of this image were distributed to some 150 U.S. planetariums, science centers and others as part of the International Year of Astronomy 2009 activities.

In celebration of the International Year of Astronomy 2009, NASA's Great Observatories -- the Hubble Space Telescope, the Spitzer Space Telescope, and the Chandra X-ray Observatory -- have collaborated to produce an unprecedented image of the central region of our Milky Way galaxy.

In this spectacular image, observations using infrared light and X-ray light see through the obscuring dust and reveal the intense activity near the galactic core. Note that the center of the galaxy is located within the bright white region to the right of and just below the middle of the image (labeled Sagitarrius A when you roll your mouse over the above composite image). The entire image width covers about one-half a degree, about the same angular width as the full moon.

Each telescope's contribution is presented in a different color:

- Yellow represents the near-infrared observations of Hubble. They outline the energetic regions where stars are being born as well as reveal hundreds of thousands of stars.

- Red represents the infrared observations of Spitzer. The radiation and winds from stars create glowing dust clouds that exhibit complex structures from compact, spherical globules to long, stringy filaments.

- Blue and violet represents the X-ray observations of Chandra. X-rays are emitted by gas heated to millions of degrees by stellar explosions and by outflows from the supermassive black hole in the galaxy's center. The bright blue blob on the left side of the full field image is emission from a double star system containing either a neutron star or a black hole.

When these views are brought together, this composite image provides one of the most detailed views ever of our galaxy's mysterious core.

To view all the different wavelengths and to learn more click on this link:
http://chandra.harvard.edu/photo/2009/galactic/

Cassiopeia A: Carbon Atmosphere Discovered On Neutron Star



• The neutron star at the center of Cas A is found to have an ultra-thin carbon atmosphere.

• This atmosphere is uniformly distributed across the neutron star, explaining why there are no pulsations detected from this object.

• The neutron star in Cas A was first detected over ten years ago in Chandra's "First Light" image.

This Chandra X-ray Observatory image shows the central region of the supernova remnant Cassiopeia A (Cas A, for short) the remains of a massive star that exploded in our galaxy. Evidence for a thin carbon atmosphere on a neutron star at the center of Cas A has been found. Besides resolving a ten-year-old mystery about the nature of this object, this result provides a vivid demonstration of the extreme nature of neutron stars. An artist's impression of the carbon-cloaked neutron star is also shown.

Discovered in Chandra's "First Light" image obtained in 1999, the point-like X-ray source at the center of Cas A was presumed to be a neutron star, the typical remnant of an exploded star, but it surprisingly did not show any evidence for X-ray or radio pulsations. By applying a model of a neutron star with a carbon atmosphere to this object, it was found that the region emitting X-rays would uniformly cover a typical neutron star. This would explain the lack of X-ray pulsations because this neutron star would be unlikely to display any changes in its intensity as it rotates. The result also provides evidence against the possibility that the collapsed star contains strange quark matter.

The properties of this carbon atmosphere are remarkable. It is only about four inches thick, has a density similar to diamond and a pressure more than ten times that found at the center of the Earth. As with the Earth's atmosphere, the extent of an atmosphere on a neutron star is proportional to the atmospheric temperature and inversely proportional to the surface gravity. The temperature is estimated to be almost two million degrees, much hotter than the Earth's atmosphere. However, the surface gravity on Cas A is 100 billion times stronger than on Earth, resulting in an incredibly thin atmosphere.

To learn more click here:
http://chandra.harvard.edu/photo/2009/cassio/