For Release: September 28, 2015
CXC
Dr. Belinda Wilkes, Director of the Chandra X-ray Center (CXC) is pleased to announce that Dr. Ralph Kraft, an astrophysicist at the Smithsonian Astrophysical Observatory and Project Scientist for the Chandra High Resolution Camera (HRC), has been appointed Principal Investigator (PI) for the science instrument. He succeeds the late Dr. Stephen Murray who was the instrument’s original PI until his untimely death in August , 2015.
The HRC is one of two science instruments used at the focus of NASA’s orbiting Chandra X-ray Observatory, one of NASA Astrophysics four Great Observatories. The HRC detects X-rays reflected from the inner surface of the assembly of 4 pairs of mirror shells. The close match of the HRC’s imaging capability to the focusing power of the Chandra mirrors produces images that reveal detail as small as one-half an arc second. This is equivalent to the ability to read a newspaper at a distance of half a mile.
The primary components of the HRC are two micro-channel plates, each consisting of a cluster of tiny lead-oxide glass tubes, with a special coating that causes electrons to be released when the inner surface of the tubes are struck by X-rays. High voltage is applied to accelerate the electrons and cause them to strike the inside of the tube, multiplying the cloud of released electrons. At the end of the tube, a crossed grid of wires detects this electronic signal and allows the position of each original X-ray to be determined with high precision. With this information, astronomers can construct finely detailed images of the hot matter in cosmic X-ray sources such as exploded stars, distant galaxies and clusters of galaxies, and very faint and distant X-ray sources.
Dr. Kraft received his undergraduate degree in Physics from the University of Pittsburgh in 1988 and his Ph.D. in Astronomy and Astrophysics from Pennsylvania State University in 1995. He joined the HRC instrument team upon completion of his doctoral thesis and worked closely with Dr. Murray and the engineering team that designed and built the flight instrument. While Dr. Kraft’s primary pre-launch role was in calibration of sub-assemblies and the flight instrument, he participated in all aspects of the development and testing of the HRC including measurements made at the X-ray Calibration Facility at MSFC, science instrument thermal/vacuum testing at Ball Aerospace in Colorado, and environmental testing of the complete satellite at TRW in California. Since the Chandra launch, Dr. Kraft has divided his time between HRC operations to ensure the health and safety of the flight instrument, ongoing analysis of in-flight calibration data, and development of his own science program. In 2013 Dr. Kraft was appointed Project Scientist for the HRC instrument team with primary day-to-day responsibility for the flight instrument.
Dr. Kraft has broad scientific interests including the study of clusters of galaxies, black holes, jets, astrophysical hydrodynamics, the formation of structure, and development of instrumentation for future mission concepts in both astrophysics and planetary science. He has written or co-authored 98 refereed and 42 contributed papers on science topics. He has been the principle investigator for 14 approved Chandra Guest Observer programs (including two large and one very large programs), 6 XMM-Newton programs, and has been a co-investigator on hundreds of other approved Chandra, XMM-Newton, HST, Spitzer, VLA, and GMRT programs.
"Our CXC team has worked with Dr. Kraft for 20 years", said Dr. Wilkes, "and I am very pleased that the HRC will be in such capable hands going forward."
Media contacts:
Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
617-496-7998
mwatzke@cfa.harvard.edu
Revised: June 08, 2022