Galileo OS SIS ICD.indd - GSA - Europa
Galileo OS SIS ICD.indd - GSA - Europa
Galileo OS SIS ICD.indd - GSA - Europa
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Table 79. Almanac Parameters<br />
* Parameters so indicated are two’s complement, with the sign bit (+or-) occupying the MSB<br />
** The F/NAV almanac transmitted by the E5a-I componenet contains the signal health status<br />
SVB status(E5aB HS) coded on 2 bits. The I/NAV almanac transmitted by the E5b-I and E1-B components<br />
contains both signal health status SVB status(E5b HS) and SVB status(E1B HS) coded on 2 bits each.<br />
*** Note that the ‘semi-circle’ is not a SI unit but can be converted as: 1 semi-circle = π radian<br />
5.1.11. Signal In Space Accuracy<br />
5.2. SAR Data<br />
Parameter Defi nition Bits<br />
a f0<br />
a f1<br />
Satellite clock correction bias<br />
“truncated”<br />
Satellite clock correction linear<br />
“truncated”<br />
SV status** Satellite signal health status 2 (F/NAV)<br />
4(I/NAV)<br />
Total Satellite Almanac Size 131(F/NAV)<br />
133(I/NAV)<br />
The signal In Space Accuracy (<strong>SIS</strong>A) defi nition will be published in a future update of<br />
this <strong>SIS</strong> <strong>ICD</strong>.<br />
Each Return Link Message encapsulated in a SAR data page contains the following<br />
data<br />
● Beacon ID (60 bits). This fi eld is used by the beacon to discern whether the RLM<br />
received is addressed to itself or to some other beacon<br />
● Message code (4 bits) defi ning the message type<br />
● Parameters fi eld (16 bits for the short RLM, 96 bits for the long RLM). This fi eld<br />
provides the information that SAR operators wish to send to the <strong>Galileo</strong>-equipped<br />
beacon.<br />
Short RLMs are used to provide the activated <strong>Galileo</strong>-equipped beacon with a short<br />
acknowledgement or various kinds of commands (e.g. to reduce its transmission rate).<br />
Long RLMs are intended for more complex commands in which several parameters may<br />
be required (e.g. to contain operational information or the coordinates of a location).<br />
© European Union 2010<br />
Document subject to terms of use and disclaimers p. ii-iii<br />
OD <strong>SIS</strong> <strong>ICD</strong>, Issue 1, February 2010<br />
Scale<br />
factor<br />
Unit<br />
16* 2 -19 s<br />
13* 2 -38 s/s<br />
NA dimensionless<br />
IOD a Almanac Issue Of Data 4 NA dimensionless<br />
t 0a Almanac reference time 10 600 s<br />
WN a Almanac reference Week Number 2 1 week<br />
Total Almanac References Size 16<br />
55
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