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Spacecraft Simulator (SPSIM) 4.0
Hassan Siddiqui and Jorgo Bakker
January 12, 2005
This is a paper version of the SPSIM help. If possible, refer to the HTML version, which contains images
and hypertext links.
SPSIM forms part of the XMM-Newton Science Simulator SciSim for the XMM-Newton satellite. Its
role is to simulate Spacecraft e ects of the satellite.
This document contains information speci c to SPSIM only; for generic information about SciSim, see
the SciSim User Guide.
1

XMM-Newton Science Simulator Page: 2
Contents
1 Overview 3
2 Usage 3
3 Con guration 3
3.1 startObs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2 exposureTime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.3 seed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.4 orbit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.5 proposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.6 observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.7 schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.8 exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.9 spacecraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.9.1 attitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.9.2 spacecraft e ects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.9.2.1 jitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.9.2.2 drift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.9.2.3 slew . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

XMM-Newton Science Simulator Page: 3
1 Overview
SPSIM is the front-end of all SciSim simulators. It produces an attitude history of the Spacecraft, which
act as input to OSIM and GSIM. Furthermore, the output can be converted into a Spacecraft Attitude
History le by using the ODF convertershodf.
2 Usage
The following command illustrates how to execute SPSIM from the command line:
spsim --exposureTime 10000 > spsim.out
In this example, exposureTime is the total exposure time, during which the Spacecraft e ects must be
calculated.
3 Con guration
The con guration can be modi ed by using the SPSIM GUI, or editing a copied SPSIM section of
the SciSim con guration le, scisim.cfg, by using a customized con guration le, which can be speci ed
on the command line using the -c option (see the SciSim User Guide), or by specifying the parameters
explicitly on the command line using the `--' pre x. For example, to set the exposure time from the
command line.
To use the GUI, rst invoke SciSimand select the `Con gure' drop-down menu. Click on the icon labelled
`S/C' using the right mouse button.
The keywords which may be speci ed, are:
3.1 startObs
Takes a string as argument, the string can be either 'now' or a valid date and/or time of the format
YYYY-MM-DD[THH:MM[:SS].
3.2 exposureTime
Duration of the exposure, for which the simulator must generate attitude information (seconds).
The rst time tag is determined by startObs(Sec. 3.1).
3.3 seed
Positive integer value specifying the seed. If 0 the current processor time is taken as start seed.
The seed is used by the random number generator to calculate e.g. the jitter e ects.

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3.4 orbit
The orbit (revolution number) [1].
3.5 proposal
The proposal which contained the observation [1].
3.6 observation
The observation within proposal [1].
3.7 schedule
Speci es whether the exposure was scheduled (S) or unscheduled (U) [1].
3.8 exposure
exposure number within the observation [1].
3.9 spacecraft
This section of the con guration speci es the initial attitude and spacecraft e ects.
3.9.1 attitude
The attitude is speci ed by three values, denoting right ascension,declination and Astronomical
position angle (all in degrees).
3.9.2 spacecraft e ects
Simple spacecraft e ects can be modeled by SPSIM.
Drift models the movement of the spacecraft pointing along a great circle, Jitter, a random walk starting
from the spacecraft pointing, and slew, a gradual change in the spacecraft position also along a great
circle.
All these e ects can be combined.
3.9.2.1 jitter
stepsize The stepsize for the random walk modeled by the jitter component (deg)

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frequency The rate of change of direction during the random walk [Hz].
3.9.2.2 drift
velocity The drift velocity (deg s 1 )
angle The direction of motion, with respect to the spacecraft +Z axis (deg).
3.9.2.3 slew
velocity The slew velocity (deg s 1 )
angle The direction of motion, with respect to the spacecraft +Z axis (deg).
Typical values for drift and jitter expected during normal XMM-Newton operation based on simulations
[2] are
 Drift : velocity 4  10 7 deg s 1
 Jitter : stepsize 1:6  10 2 =sqrt< ExposureTime > deg, frequency 8  10 3 Hz
References
[1] ESA. XMM interface control document: Observation and slew data les (xscs to ssc) (scisim to
socsim). Technical Report XMM-SOC-ICD-0004-SSD Issue 2.2, ESA/SSD, May 1999.
[2] ESA. XMM experiment interface document (part A). Technical Report RS-PX-0016 Issue 6,
ESA/PXP, February 1996.