Science Verification Analysis and Calibration (SVAC) Plan
Eduardo do Couto e Silva
Last update February 04, 2003
The SVAC Plan
The GLAST LAT SVAC Plan, is driven by the LAT Science Requirement Document and consists of pre and post-launch activities. The pre-launch activities are divided according to the available hardware at different phases of integration, whereas the post-launch activities consists of Phase 0 only, after which a working instrument is delivered to IOC.
This activity, which is also part of the Beam Test Plan (LAT-TD-00444), is
designed to verify with what accuracy the MC simulations reproduce the
performance of the LAT. As shown in
the diagram below, instrument calibrations must be performed prior to final MC
Verification of Science Requirements Science
Verification on the ground is done during the particle beam tests.
Measurements are performed at a limited, but well defined, number of
points in the LAT parameter space (see Beam Test Plan LAT-TD-00444 for further
details). The required accuracy for each of these measurements is specified in
LAT-PS-00010-1. Once validated, the
MC simulations will then be used to estimate the performance of the LAT
instrument at any point of the LAT parameter space. With a validated MC,
the SAS group will produce the Instrument Response Functions.
Calibration data will be obtained from
three hardware units
Engineering Model (EM) single tower not fully
Calibration Unit (CU)
four-tower unit fully instrumented
LAT sixteen-tower unit
fully instrumented, flight hardware
The SVAC plan builds
progressively on the knowledge acquired from testing single units and retesting
after multiple towers have been assembled together. These hardware units are
tested with either cosmic rays and/or particle beams. The next section outlines
the focus of each hardware unit test.
One of the key elements of
the calibration program is to perform data analysis for instrument calibrations
and MC Verification. This is also discussed later in this note. The figure below
shows the interdependence of the different parts of the program. Science
Verification depends on information from both High and Low Level Calibrations
and Software Performance tests. Prior to any test of the SVAC Plan we assume
that the hardware has successfully passed the functional tests.