The X-ray Calibration Facility  played host to AXAF integrated calibration in Fall 1996 and Spring 1997.  Built specifically for AXAF calibration, the XRCF enabled scientists to approximate x-ray point sources:  a feature which was critical to proper calibration of the AXAF High Resolution Mirror Assembly (HRMA).  In this picture, 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 inside the building in the foreground.

The ACIS team collected calibration data utilizing the HRMA telescope during three data collection intervals. Following the XRCF nomenclature these occured during Phases 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).
 

Phase	Detector	Mirror	Start Date	End Date
F	ACIS-2C	HRMA	22 Feb 1997	10 Mar 1997
G	ACIS-2C	HRMA	10 Apr 1997	12 Apr 1997
H	ACIS Flight	HRMA	17 Apr 1997	18 May 1997
I	ACIS Flight	None	7 May 1997	19 May 1997

 
During all phases of ACIS calibration at XRCF, 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).