more review of requirements
DESCRIPTION
MORE Review of Requirements. L. Iess. With WVR. Dish deformations not included. Proposed configuration of the onboard radio system. DST. XTWTA. 8.4 GHz. 7.2 GHz. KaTWTA. 32.5 GHz. MORE. KAT+SSA. 34.3 GHz. 32.5 GHz. X Ka. X Ka. - PowerPoint PPT PresentationTRANSCRIPT
MOREReview of Requirements
L. Iess
Allan Standard Deviation budget
Error Source Allan deviation @103 s Propagation Media Total: 10–14
Plasma 3×10–16 * Troposphere 10–14 *** Ionosphere <3×10–16 * Ground System Sub-total: 6.2×10–15 Frequency Standard 10–15
Receiver Chain 3×10–17 *
Transmitter Chain 3×10–16 *
Thermal and mechanical deformation 6×10–15 Station Location 1.2×10–15 Earth Solid Tides 4×10–16 * Spacecraft Sub-total: 8×10–15 Uncertainty of the HGA motion about the spacecraft centre of mass
4×10–16 *
DST 2×10–15 KaT 10–15 TWTA 5×10–17 * High-Gain Antenna assembly thermo-mechanical stability **
6.7×10–15
Uncertainty of MPO angular rate 10–15
Total 1.4×10–14 *
With WVR
Dish deformationsnot included
Proposed configuration of the onboard radio system
X Ka X KaKAT+SSA
XTWTA
KaTWTA
DST7.2 GHz
34.3 GHz
8.4 GHz
32.5 GHz
• No intermodulation, larger output power, larger data rate• Simpler testing procedures• Onboard range delay calibration• Simpler interfaces
32.5 GHz
MORE
Target accuracy:
f/f = 10-14 at 103-104s = 10 cm
y(1000s)=10-14 1.5 micron/s
1.5 mm in 1000 s
Plasma noise cancellation
Multi-frequency radio link (two-way)
Target accuracy:
f/f = 10-14 at 103-104s = 10 cm
KAT
XSSA
KaTWTA
DST7.2 GHz
34.3 GHz
X Ka X Ka
8.4 GHz
32.5 GHz
y=10-14 is equivalent to a one-way range rate of 1.5 micron/s
The corresponding one-way displacement in 1000 s is 1.5 mm
Original configuration – MORE EID-B
Cancellation of plasma noise with a multifrequency link
[Bertotti, Comoretto, Iess, 1993]
2
1
XXndXX
2
1
XKndXK
222
11
KK
ndKK
X/X Doppler/range observable
X/Ka Doppler/range observable
Ka/Ka Doppler/range observable
Three unknown quantities: • non-dispersive term ( ) • uplink plasma ( )• downlink plasma ( )
nd
749
880
_
_ UX
DXXX f
f
749
3344
_
_ UX
DKXK f
f
15
14
_
_ UK
DKKK f
f UXUK ff __ /
Cancellation of plasma noise (cont.)
XKXXKKnd 35
1
13
1
XKXX 67.067.0
XKXXKK 05.1101.105.1 3
Conclusion:
The Ka/Ka link provides the crucial observable and needs the highest accuracy.