EN 16603-60-20-2020 pdf download.Space engineering-Star sensor terminology and performance specification.
NOTE 3 Guidelines and clauses for robustness to solar events are proposed in clause 5.13.
b. The maximum magnitude of body rate shall be used.
NOTE The maximum body rate is the worst case condition for most missions. For specific cases, the
worst case can be adapted, e.g. to include jitter.
c. The supplier shall identify the worst case projection in BRF of the value defined in 5.4h.
NOTE Different angular rates can be specified with associated required performance.
d. The maximum magnitude of angular acceleration shall be used.
NOTE The maximum angular acceleration is the worst case condition for most missions. For specific cases, the worst case can be adapted, e.g. to include jitter.
e. The supplier shall identify the worst case projection in BRF of the value de-fined in 5.4d.
NOTE Different angular accelerations can be specified with associated required performance.
For multiple head configuration the worst case conditions of angular rate and stray light of each optical head shall be discussed and agreed between supplier and customer.
g. Single star position measurement performance within the verification simulations shall be:
1. validated against on-ground test data for fixed pointing conditions, and
2. able to predict metric performance under these conditions with an accuracy of 10 %.
h. If test data is available for the individual error sources, the simulation shall be validated against this data with an accuracy of 10%.
Detector error sources in the simulation shall also be validated using direct data injection into the electronics and analysis of the test outputs.
5.5 General performance metrics
5.5.1 Overview
Clause 5.5 presents the general performance metrics for the error contributing to the star sensor performances. In Annex F!, an example of data sheet built on the performance metrics is given.
5.5.2 Bias
5.5.2.1 General
a. A confidence level for the bias shall be specified by the customer.
b. The Ensemble interpretation shall be used.
NOTE The Ensemble interpretation is described in Annex
E.2.
c. The bias performance shall be specified for a defined ambient temperature.
NOTE The initial alignment is an instantaneous measurement error at the time of calibration. For the purposes of error budgeting it can be considered to be an invariant error.
5.5.2.2 Contributing error sources
a. The following types of error source shall be included:
I. On-ground calibration error between the sensor Alignment Reference Frame (ARF) and the sensor Boresight Reference Frame
(BRF).
2. Launch induced mis.alignments of BRF with respect to MRF.
NOTE 1 This arises typically from accuracy limitations
within the measurement apparatus used to
perform the calibration.
NOTE 2 Refer to the Annex G for the contributing error sources description.
5.5.2.3 Verification methods
a. The calibration shall be performed via ground-based test using an optical bench set-up to determine the sensor Alignment Reference Frame (ARF)- sensor Boresight Reference Frame (BRF) alignment.
b. The bias error shall be validated by analysis, test or simulation, taking into account calibration test bench accuracy.
NOTE I Initial alignment verification cannot be done without verification of the measurement accuracy
of the set-up used for calibration.
NOTE 2 E.g. “The Star Sensor initial alignment shall have an initial alignment error (X-, V-axes rotation) of less than 10 arcsec at a quoted ambient temperature (the temperature during alignment).”
5.5.3 Thermo elastic error
5.5.3.1 General
a. A confidence level for the thermos elastic error shall be specified by the customer.
b. The ‘Ensemble’ interpretation shall be used.
NOTE The ‘Ensemble’ interpretation is described in AnnexE.2
5.5.3.2 Contributing error sources
a. Error sources that gradually change the alignment of the sensor Mechanical Reference Frame (MRF) and the sensor Boresight Reference Frame (BRF) from the start of the in-flight mission shall be included.
NOTE I E.g. “The thermal sensitivity to temperature of line of sight stability shall be less than 1 arcsec/Kek’in.”
NOTE 2 Refer to the Annex C for the contributing error sources description.
5.5.3.3 Verification methods
a. Thermally induced error contributions to the thermo elastic error shall be verified by the use of thermal models supported and validated by ground test results performed under thermal vacuum conditions.
5.5.4 FOV spatial error
5.5.4.1 General
a. A coniidence level tor the kUv spaiiai error shall be specified by the customer.
b. The ‘Ensemble’ interpretation shall be used.
NOTE The Ensemble interpretation is described in Annex
E.2.
c. The performance shall be specified under the related performance general conditions.
d. The error classification of the FOV spatial error shall be discussed and agreed between supplier and customer.
NOTE The temporal behaviour of the FOV spatial error is a function of the star velocity across the
STR field of view.EN 16603-60-20-2020 pdf download.