Penn State University
The Chandra was launched aboard the Space Shuttle Columbia July 23, 1999.  


The X-ray Calibration Facility (XRCF) hosted the AXAF integrated calibration in 1996-1997. Built specifically for AXAF calibration, the XRCF enabled scientists to approximate x-ray point sources, which was critical to proper calibration of the AXAF High Resolution Mirror Assembly (HRMA).

The x-ray source building is a small cube-shaped building located at the start of the quarter mile guide tube.  The vacuum chamber and clean room are located at the end of the guide tube in the building in the foreground.

The calibration data was collected with the HRMA telescope during three intervals; Phase F, G, and H.
During Phases F and G the HRMA focussed X-rays were collected on two flight-like CCDs (one front side illuminated (FI), and one back side illuminated (BI)) in a camera utilizing electronics very similar to the MIT CSR lab cameras. This camera, named the ACIS-2C, served as a proxy to enable data collection while the ACIS flight instrument finished the final stages of certification and thermal vacuum testing.  During Phase H  the ACIS flight camera was calibrated with the HRMA telescope in place.  Following the departure of the HRMA mirrors to meet the schedule of assembly into the spacecraft, the XRCF was used to collect data with ACIS without any focussing optics (Phase I).




Start Date

End Date




22 Feb 1997

10 Mar 1997




10 Apr 1997

12 Apr 1997


ACIS Flight


17 Apr 1997

18 May 1997


ACIS Flight


07 May 1997

19 May 1997

During all phases data was collected via a High Speed Tap interface.  The high-speed tap (HST) pipeline acquired raw, complete CCD frames directly from the  camera using a data pathway that is available only on the ground.  An archive of HST event lists is maintained by the Calibration Group at the AXAF Science Center.

A second data path used during phases H and I was an emulation of the on-orbit telemetry system.  The telemetry pipeline acquired events that were recognized by the ACIS flight software and telemetered through a telemetry emulation system.  The telemetry data was processed into FITS events list by a program written by Penn State engineers and called ATICA.  These event lists were processed in near real time by the TARA analysis software to ensure data quality.  TARA is an easy-to-use interactive IDL widget program used to analyze x-ray event lists for ground-based data.  An archive of Phase H telemetry events is maintained by  the ACIS Calibration group at Penn State.

For a more complete description of ACIS calibration, see the ACIS Calibration Report.  For a complete description of the ACIS CCD Camera, see the Science Instrument Operations Handbook (SOP-01).

ACIS Animation:  Raw Intensities

This image shows a series of X-ray images collected during the calibration of the ACIS instrument. These data were collected with the AXAF telescope (HRMA) image deliberately out-of-focus, so that the X-rays from the four concentric telescope mirrors appear as four concentric rings. Because the outer mirrors focus only low energy X-rays and the inner mirrors focus all energies up to about 10 keV, the outer rings disappear as the energy of the X-ray beam is increased.


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The PSU ACIS web-pages are maintained by Bertil Olsson. Last update 10/18/2000