Download VEX design report - TOC

Ref
: VEX-T.ASTR-TCN.00349
Issue : 2
Rev. : 0
8.3
Date
: 06/02/2004
Page
: 8.3
TT&C CONFIGURATIONS ACCORDING TO THE MISSION PHASES
In the LEOP phase, communications are done in S-band via the LGAs.
When the LEOP phase is completed (few days after Launch), communications are done in X-Band via
one HGA. The proper HGA is selected along the mission depending on the planets configuration to
avoid sun illumination on the cryo face (-Xs) as illustrated on the following figure.
End of Mission
0.8
0.6
HGA switching
Start
2nd Venus day
Quadrature
.
.
0.4
0.2
HGA2 selected on
Inferior Conjunction side
0.0E
0.0
-0.2
0.2
Inferior
Conjunction
0.4
.
0.6
0.8
S
1.0
1.2
Superior
Conjunction
1.4
1.6
.
HGA1 selected on
Superior Conjunction side
1.8
Start
4th Venus day
Start 3rd
Venus day-0.4
Quadrature
-0.6
.
.
HGA switching
-0.8
AU
VOI
Start of science
Figure 8.1.2 : VEX HGA selection along the mission
The following table sums up the communication strategy along the mission.
Mission Phase
Earth to SC distance
RF Band
HGA1
HGA2
< 0.05 AU (TBC)
S-Band
√
√
-
-
Near-Earth Commissioning
X-Band
-
-
-
√
Cruise
X-Band
-
-
-
√
VOI
X-Band
-
-
√
√
Payload Commissioning
X-Band
-
-
√
-
< 0.78 AU
X-Band
-
-
-
√
0.78 AU<d<1.72 AU
X-Band
-
-
√
-
LEOP
Routine
and
Operations
Extend
LGA1
LGA2