XRCF
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).
|
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 |
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).
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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