# Presentation: 268668

## XRS Calibration

**XRS Calibration**
- Status & In-Flight Plan

**Energy Scale**
**Line Spread Function**
**Effective**** Area**
**Background**

## The energy scale is a complicated, non-analytic function.   Using a physical model for the pulses, we find that E(V) can be well characterized by a 4th order polynomial.  For ground calibration data this gives an energy scale that is accurate to E    0.5 eV

- The energy scale is a complicated, non-analytic function.   Using a physical model for the pulses, we find that E(V) can be well characterized by a 4th order polynomial.  For ground calibration data this gives an energy scale that is accurate to E    0.5 eV

## Energy Scale: In-Flight 

- The energy scale must be re-established in-flight.  We will use offset pointings of Capella and GX301-2 to illuminate all pixels.

| Line
 | Energy
(keV) | Inner
Pixel | Outer
Pixel |
| --- | --- | --- | --- |
| N VII Ly | 0.500 | 105 | 58 |
| O VIII Ly | 0.654 | 1045 | 404 |
| Ne X Ly | 1.022 | 1051 | 407 |
| Mg XII Ly | 1.473 | 279 | 108 |
| Si XIV Ly | 2.006 | 70 | 27 |
| K K | 3.314 | 186 | 186 |
| Mn K | 5.894 | 6200 | 6200 |
| Fe K | 6.400 | 3320 | 1262 |
| Ni K | 7.461 | 105 | 40 |

## Energy Scale: Drift Correction

- 17K IF = 14.875 K
- ADR CP = 1.254 K

- 17K IF = 15.050 K
- ADR CP = 1.230 K

- 17K IF = 15.480 K
- ADR CP=1.226 K

- Changes in the energy scale will be tracked using an offset pixel.
- During ground calibration we discovered that the calibration pixel and the array pixels respond differently to changes in the thermal environment.
- This is very difficult to characterize.  For small changes in temperature, the drift is linear.
- 	Cal Pixel:
- 	TNe ~ 40 eV/K
- 	THe ~ 130 eV/K

## Line Spread Function

- The line spread function is well characterized by a Gaussian function.
- This resolution kernel is measured using a 55Fe source.  For the most flight-like conditions we find:
- 	Composite:	EFWHM ~ 5.6 eV
- 	Pix mean:	EFWHM ~ 5.3 eV
- 	Std dev:	 ~ 0.2 eV
- The energy dependence appears to follow the predictions of the pulse model.

## There is a low energy shoulder due to photo- and electron-escape events.  A monte-carlo is being developed.  It depends on both the photoelectric absorption cross-sections and the electron interaction with the solid state HgTe absorber. 

- There is a low energy shoulder due to photo- and electron-escape events.  A monte-carlo is being developed.  It depends on both the photoelectric absorption cross-sections and the electron interaction with the solid state HgTe absorber.

## Aeff = Atel * tel * filters * intercept * QE * electonics

- Aeff = Atel * tel * filters * intercept * QE * electonics

- Telescope: Described by Kai-Wing Chan
- Blocking Filters: Aluminum and oxides in the filters produce absorption structure at low energies.  This is measured on the ground.
- Pixel Intercept: This will depend on the boresight, the telescope PSF and the alignment of the pixels.
- Absorber Quantum Efficiency:  This depends on the column density of the HgTe absorbers.  The absorbers have been measured and weighed, and the Hg L absorption edges have been measured.
- Electronics: At high count rates some events will not be identified by the pulse detection algorithms.  This ‘pile up’ will decrease the effective area by a few percent.

## Effective Area: Components

- Filter Transmission

- Quantum Efficiency

## Effective Area: In-Flight

**Al K Edge**

- The goal of the in-flight calibration is to verify the discrete structure and characterize the global effective area.  We will use the bright, featureless BL Lac 3C273 as a backlight.  Simultaneous observations and cross-calibration with XMM-Newton/Chandra are required.

## Effective Area: In-Flight

- To monitor the presence of ice contamination on the blocking filters we will observe line-rich SNRs N132D and 1E0102-72 repeatedly during the early phases of the mission.

**              ****N132D**
_**Line            E (keV)  Cts **_
- N VII Ly	0.500	65
- O VIII Ly	0.654	1900
- O VIII Ly	0.775	850
- Ne Ly	1.022	2500
- Mg Ly	1.472	500

## Background

- Primary cosmic ray protons:  The anticoincidence detector identifies all but ~0.1% of events due to primary protons.  Protons that hit the frame cause simultaneous pulses on multiple pixels that can be rejected by the processing software.
- Secondary electrons and photons: To estimate the unrejected background due to secondary events, we scale the ASCA rate  7 x 10-4 events/s.