- An advanced tool for LEOP support -
OPS-G FORUM
20/03/2009

PART1 - Overview of requirement and Technical implementation
Piermario Besso: H/OPS-GSA
– What is XAA?
– Why do we need XAA?
– Requirements
– Alternative solutions?
– A challenging trade-off
– Design
– Factory acceptance tests
PART2 - On-site installation and validation
Filippo Concaro: OPS-GSA
– On-site installation
– Alignment
– Site Acceptance tests
– XAA system tests
OPS-G FORUM - 20/03/2009 2

•The acquisition and tracking range of a reflector
antenna is proportional to its beam size, which is
inversely proportional to its diameter and the signal
frequency
•The XAA system makes use of a 1.3 m dish to
enlarge the acquisition range of ESTRACK 15 m
antennas
•The two antennas shares the SERVO system, the
switchover from one tracking system to the other is
managed at Front End Controller (FEC) level.
OPS-G FORUM - 20/03/2009 3

LISA Pathfinder (Rockot launcher)
3σ dispersion from Perth
1,1
•New missions will not use S-band (2 1,0
0,9
GHz), but X-Band (8 GHz) for LEOP. 0,8
0,7
0,6
0,5
•The beam in X-band is 4 times smaller 0,4
0,3
than S-Band
Elevation pointing Error
0,2
0,1
0,0
•The tracking range of the ESTRACK -0,1
-0,2
15m antennas is too small to cover the -0,3
-0,4
foreseen dispersion area -0,5
-0,6
-0,7
-0,8
•The actual 15m antenna search -0,9
function is too slow to cope with the -1,0
-1,1
-1,1 -1,0 -0,9 -0,8 -0,7 -0,6 -0,5 -0,4 -0,3 -0,2 -0,1 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1
spacecraft’s speed during LEOP Cross-Elevation Pointing Error
Within 15m tracking range (8.1%)
Within XAA Tracking Range (99.8%)
Outside XAA tracking range (0.2%)
(In order to cover this latter cases one could use the search function with the XAA antenna)
OPS-G FORUM - 20/03/2009 4

• Acquisition beam width: >2°
• Minimum Power Flux Density: -148 dBW/m2
• Maximum Modulation Loss: 15 dB
• Time to achieve autotrack <10 sec
(switchover to main antenna not included)
OPS-G FORUM - 20/03/2009 5

Fast Search:
Improve the already
implemented search function of
the 15m antennas in order to
have the beam scanning a larger
area in a shorter time
Not compliant in terms of maximum time required to acquire
(Worst case: 40 sec)
OPS-G FORUM - 20/03/2009 6

• In order to achieve a tracking range sufficiently
wide the antenna diameter has to be as small
as possible
• In order to get a figure of merit (G/T) sufficient
to cope with the other requirements the antenna
diameter has to be adequately large
As best trade off a diameter of 1.3 m has been chosen
OPS-G FORUM - 20/03/2009 7

• In order to achieve the challenging G/T requirements
for such a small antenna state of the art technologies
have been selected for the XAA design:
1. Shaped main and sub reflectors
2. Optimised Corrugated feed-horn
3. Wave guide feeding system
4. Very low noise amplifiers
5. Compact outdoor down converter
6. Temperature controlled outdoor box
7. Last generation Tracking Receiver
OPS-G FORUM - 20/03/2009 8

OPS-G FORUM - 20/03/2009 9

The impact of the gravity deformations have been thoroughly analysed both in terms of:
•XAA Pointing error
•Impact of XAA Antenna on 15m antenna pointing error
Elevation 0° 30° 60° 90°
AZ error [mdeg] 0 4 7 8
EL error [mdeg] 0 -4 -16 -32
TOT error [mdeg] 0 6 17 33
XAA Pointing errors wrt Antenna Elevation
Elevation 0° 30° 60° 90°
AZ error [mdeg] 0/3 0/1 0/0 0/0
EL error [mdeg] 27/30 24/26 14/15 0/-3
TOT error [mdeg] 27/30 24/26 14/15 0/3
15m Pointing errors wrt Antenna Elevation w/o and with XAA
OPS-G FORUM - 20/03/2009 10

Due to the considerable XAA-DC power dissipation the XAA Outdoor
box had to be temperature controlled to keep it within the operational
temperature range of the LNAs.
This has been achieved by means of a
protective sun-shield and two Peltier
elements
XAA LNAs Thermal analysis
Sun-Shield
XAA DC Thermal analysis
OPS-G FORUM - 20/03/2009 11

XAA FAT has taken place at Eads
ASTRIUM Compact Range facilities in
Ottobrunn (D)
During the FAT
Compliance with respect
to the specification for
all RF components has
been proven
XAA Tracking patterns for all operation frequencies
OPS-G FORUM - 20/03/2009 12

OPS-G FORUM - 20/03/2009 13

Supporting structure Antenna
Outdoor Equipment box Counterweights
OPS-G FORUM - 20/03/2009 14

Correct XAA-15m antennas alignment is crucial
Specified alignment accuracy is 30 mdeg
Alignment procedure
consists of 3 steps:
1. Mechanical alignment
2. RF alignment
(Calibration tower)
3. RF alignment verification
on spacecraft
OPS-G FORUM - 20/03/2009 15

Rough alignment at 90° Elevation
Fine alignment at 0° Elevation
OPS-G FORUM - 20/03/2009 16

70,0
The distance between the XAA and 60,0
the 15m antenna electrical centres (L)
50,0
is not negligible with respect to the
antenna – Calibration tower distance 40,0
(D), this results in an angular offset
Antenna Gain (dBi)
30,0
(θ), which has to be taken into account
for the RF alignment and the 20,0
acceptance tests 10,0
0,0
Alignment goal:
-10,0
0.110°±0.03° offset in Azimuth
0 ° ±0.03° offset in Elevation -20,0
θ
-30,0
-0,400 -0,300 -0,200 -0,100 0,000 0,100 0,200 0,300 0,400
Offset from Boresight direction (deg)
XAA SUM XAA DELTA 15m DELTA 15m SUM
L = 8.5 m
θ = 0.110°
θ = atan(L/D)
D = 4400 m
OPS-G FORUM - 20/03/2009 17

PER1 15m antenna - X-Band
• Measurement on calibration Tracking Null Positions on Calibration Tow er
(Measurement accuracy ~10 mdeg)
tower are affected by 0,890
0,880
several factors: 0,870 Plank Herschel
0,860
1. Deformation of antenna 0,850
Elevation (deg)
0,840
mechanical structure due to 0,830
Lisa PF RHC Lisa PF LHC
0,820
gravity 0,810
0,800
2. Multipath and fading effects 0,790
0,780
due to ground reflections 0,770
0,760
15 meter antenna null 0,750
0,740
position on Calibration
202,860
202,870
202,880
202,890
202,900
202,910
202,920
202,930
202,940
202,950
202,960
202,970
202,980
202,990
203,000
203,010
203,020
203,030
203,040
203,050
203,060
203,070
203,080
Tower “moves” with
Azimuth (deg)
frequency and polarisation
RHC LHC
XAA-15m RF alignment on Calibration Tower is frequency dependant
OPS-G FORUM - 20/03/2009 18

RF Alignment on Calibration Tower is optimised for Lisa Pathfinder
(8495 MHz) frequency RHC polarisation
OPS-G FORUM - 20/03/2009 19

RF Alignment on Calibration Tower for LPF frequency, RHC
Perth X-Band 15m and XAA
Tracking (Delta) Null and Sum pattern Peak positions
0,920
0,910
The enlarged points
0,900
0,890 are the ones for 8495
0,880 MHz (Lisa Pathfinder)
0,870 15m SUM RHC
RHC
0,860 15m DELTA RHC
0,850 15m SUM LHC
Elevation (deg)
0,840
15m DELTA LHC
0,830
XAA SUM RHC NF
0,820
0,810 XAA DELTA RHC NF
0,800 XAA SUM LHC NF
0,790 XAA DELTA LHC NF
0,780 XAA SUM RHC FF
0,770
XAA DELTA RHC FF
0,760
0,750 XAA SUM LHC FF
0,740 XAA DELTA LHC FF
0,730
0,720 15m antenna tracking range
0,710
0,700
202,85
202,86
202,87
202,88
202,89
202,90
202,91
202,92
202,93
202,94
202,95
202,96
202,97
202,98
202,99
203,00
203,01
203,02
203,03
203,04
203,05
203,06
203,07
203,08
203,09
203,10
Measurement Accuracy is:
±5 mdeg for 15m delta null and sum peak
Azimuth (deg) ±15 mdeg for XAA delta null
±30 mdeg for XAA sum peak
OPS-G FORUM - 20/03/2009 20

RF Alignment on Calibration Tower for LPF frequency, LHC
Perth X-Band 15m and XAA
Tracking (Delta) Null and Sum pattern Peak positions
The enlarged points
0,920
are the ones for 8495
0,910 MHz (Lisa Pathfinder)
0,900 LHC
0,890
0,880
0,870 15m SUM RHC Even if affected by the
0,860
15m DELTA RHC mentioned disturbance
0,850
15m SUM LHC factors, the graph
Elevation (deg)
0,840
0,830 15m DELTA LHC shows that also for
0,820 XAA SUM RHC NF LHC polarisation the
0,810 XAA DELTA RHC NF
XAA tracking null
0,800 XAA SUM LHC NF
0,790
position corrected by
XAA DELTA LHC NF
0,780
XAA SUM RHC FF
the Far Field (FF) –
0,770
XAA DELTA RHC FF
Near Field (NF) offset
0,760
0,750 XAA SUM LHC FF falls within the 15m
0,740 XAA DELTA LHC FF antenna tracking
0,730
15m antenna tracking range
range.
0,720
0,710
0,700
Measurement Accuracy is:
202,85
202,86
202,87
202,88
202,89
202,90
202,91
202,92
202,93
202,94
202,95
202,96
202,97
202,98
202,99
203,00
203,01
203,02
203,03
203,04
203,05
203,06
203,07
203,08
203,09
203,10
±5 mdeg for 15m delta null and sum peak
Azimuth (deg) ±15 mdeg for XAA delta null
±30 mdeg for XAA sum peak
OPS-G FORUM - 20/03/2009 21

In the case of a spacecraft, the distance between the XAA D >> L
and the 15m antenna electrical centres (L) is negligible
with respect to the Ground Station – Spacecraft distance
(D), this results in a negligible angular offset (θ), and thus
in a perfect alignment between the two antennas
70,0
60,0
50,0 θ = 0°
40,0
Antenna Gain (dBi)
30,0
20,0
10,0
0,0
-10,0
-20,0
-30,0
-0,400 -0,300 -0,200 -0,100 0,000 0,100 0,200 0,300 0,400
Offset from Boresight direction (deg)
XAA SUM XAA DELTA 15m DELTA 15m SUM
OPS-G FORUM - 20/03/2009 22

Spacecraft GEOTAIL ERS2 ENVISAT
Agency JAXA ESA ESA
Frequency [MHz] 8474.66 8040/1840 8200/8300
Tracking Mode PLL Cross Correlation Cross Correlation
Spacecraft Speed Slow Fast Fast
Flux at antenna
<-163 dBW/m2 >-133 dBW/m2 >-131 dBW/m2
(including Modulation Loss)
Availability 1 day/week at perigee 1 or 2 times/day 1 or 2 times/day
OPS-G FORUM - 20/03/2009 23

GEOTAIL Autotrack XAA-15m comparison for a 40° Elevation Pass & 120.000 km range
0,200
High dispersion due
to very low signal 0,150
Offset magnitude is 0,100
consistent with what Elevation Pointing Error (deg)
0,050
observed on the
XAA Average Null (with STDEV)
Calibration Tower 0,000
15m Average Null (with STDEV)
15m NULL
XAA NULL
-0,050
-0,100
-0,150
-0,200
-0,200 -0,150 -0,100 -0,050 0,000 0,050 0,100 0,150 0,200
Cross-elevation Pointing Error (deg)
OPS-G FORUM - 20/03/2009 24

Both ERS2 and Envisat are using X-band to dump data at high data rate.
The frequency used are:
8040 and 8140 MHz for ERS2 XAA
SUM & DELTA
8200 and 8300 MHz for ENVISAT Channel Selection
Switch
M&C
While XAA Downconverter XAA
XAA-DC
covers the band between 8025
Antenna
Spacecraft
EL
XAA-TRR XAA-SMC
to 8500 MHz, the 15m antenna Test Signal
XEL
AGC
EL
XEL
Downconverters covers only the EL XEL
AGC
AZ PLOTTER
or
Space Research band (8400- ACU EL
AGC
DATA
LOGGER
EL
8500 MHz) AGC
EL XEL
XEL
PER1 EL
TRR SMC
Antenna XEL
Frequency
Switch
M&C Switch M&C
an additional converter (mixer) had to be SUM & DELTA
LDC
AZ, EL
Switch M&C
Channel Selection EL, XEL, AGC, Lock, PLL BW, TR Mode FEC
used to translate the frequency in the required EL, XEL, AGC, Lock, PLL BW, TR Mode
Frequency
range MIXER
XDC Frequency
TEST SYNTHESIZER
TEST SETUP
OPS-G FORUM - 20/03/2009 25

ENVISAT Autotrack XAA-15m comparison for a 55° MAX Elevation Pass
0,200
Smaller dispersion
due to much higher 0,150
signal (like expected
in a LEOP scenario) Elevation Pointing Error (deg)
0,100
0,050
XAA Average Null (with STDEV)
Offset magnitude is 15m Average Null (with STDEV)
0,000 15m NULL
consistent with what XAA NULL
observed on -0,050
Program Track
GEOTAIL and on
the Calibration -0,100
Tower
-0,150
-0,200
-0,200 -0,150 -0,100 -0,050 0,000 0,050 0,100 0,150 0,200
Cross-elevation Pointing Error (deg)
OPS-G FORUM - 20/03/2009 26

• G/T
• Tracking range & tracking slope
• Acquisition range
OPS-G FORUM - 20/03/2009 27

XAA G/T at 5 and 30 deg Elevation
20,0
19,0
18,0
17,0
16,0
dB/K
15,0
Specification
14,0
13,0
12,0
11,0
10,0
8000 8100 8200 8300 8400 8500
Frequency [MHz]
RHC - LNA1 - 5 deg LHC - LNA2 - 5 deg
RHC - LNA1 - 30 deg LHC - LNA2 - 30 deg
OPS-G FORUM - 20/03/2009 28

XAA Tracking Sensitivity
•The graphs shows the 8495 MHz LHC (Lisa Pathfinder)
linearity of the tracking errors 10,00
9,00
wrt angular offset at 8495 8,00
MHz. 7,00
6,00
5,00
•Due to the fact that the 4,00
antenna beam gets narrower Tracking Error Voltages (V)
3,00
2,00
as the frequency increases, it 1,00
0,00
can be considered as a worst -1,00
case scenario. -2,00
-3,00
-4,00
•In the specified range of ±1° -5,00
-6,00
the red curve is pretty much -7,00
linear and the cross talk (blue -8,00
-9,00
curve) negligible -10,00
-1,50 -1,00 -0,50 0,00 0,50 1,00 1,50
•The tracking range extends Boresight Azimuth offset (°)
up to roughly ±1.2° DELTA X DELTA Y
OPS-G FORUM - 20/03/2009 29

The graphs below show the measured tracking slopes for different polarisations and axis
XAA Tracking Sensitivity XAA Tracking Sensitivity
8495 MHz LHC (Lisa Pathfinder) 8495 MHz RHC (Lisa Pathfinder)
10,00 10,00
9,00 9,00
8,00 8,00
7,00 7,00
6,00 6,00
5,00 5,00
4,00 4,00
Tracking Error Voltages (V)
Tracking Error Voltages (V)
3,00 3,00
2,00 2,00
1,00 1,00
0,00 0,00
-1,00 -1,00
-2,00 -2,00
-3,00 -3,00
-4,00 -4,00
-5,00 -5,00
-6,00 -6,00
-7,00 -7,00
-8,00 -8,00
-9,00 -9,00
-10,00 -10,00
-1,50 -1,00 -0,50 0,00 0,50 1,00 1,50 -1,50 -1,00 -0,50 0,00 0,50 1,00 1,50
Boresight Azimuth offset (°) Boresight Azimuth offset (°)
DELTA X DELTA Y DELTA X DELTA Y
XAA Tracking Sensitivity XAA Tracking Sensitivity
8495 MHz LHC (Lisa Pathfinder) 8495 MHz RHC (Lisa Pathfinder)
10,00 10,00
9,00 9,00
8,00 8,00
7,00 7,00
6,00 6,00
5,00 5,00
4,00 4,00
Tracking Error Voltages (V)
Tracking Error Voltages (V)
3,00 3,00
2,00 2,00
1,00 1,00
0,00 0,00
-1,00 -1,00
-2,00 -2,00
-3,00 -3,00
-4,00 -4,00
-5,00 -5,00
-6,00 -6,00
-7,00 -7,00
-8,00 -8,00
-9,00 -9,00
-10,00 -10,00
-1,50 -1,00 -0,50 0,00 0,50 1,00 1,50 -1,50 -1,00 -0,50 0,00 0,50 1,00 1,50
Boresight Elevation offset (°) Boresight Elevation offset (°)
DELTA X DELTA Y DELTA X DELTA Y
OPS-G FORUM - 20/03/2009 30

Tests on GEOTAIL
•Marginal Power Flux Density
•Offsets wrt nominal trajectory obtained applying time offset to the program track
PLL bandwidth (Hz) 3000 1000 300 100
Acquisition range (°) >±0.5 >±1 >±1.25 >±1.4
Tests on ERS2/ENVISAT
•Suppressed carrier mode
•Offsets wrt nominal trajectory obtained using ad-hoc modified STDMs
Cross correlation bandwidth (kHz) 5000 500
Acquisition range (°) >±0.750 >±1
Type of offset combined along and cross track 1° offset along or cross track 1° offset
OPS-G FORUM - 20/03/2009 31

• Various tests performed both on Spacecrafts and Calibration Tower
• Time to get lock on XAA antenna (depends on tracking BW selected and
entity of the offset): <4 sec
• Time to get stable XAA autotrack and lock on 15m antenna after XAA
autotrack has been commanded: <4 sec
Time to achieve autotrack on a signal being within the acquisition area:
<8 sec ([URD-PE-006]: 10 sec)
• Time to switch from XAA to 15m autotrack: <5 sec + decision time
• Overall acquisition process has been achieved in less than 10 sec on
GEOTAIL (time from closing the PLL loop at 1° offset wrt program track to
achieve 15m autotrack)
OPS-G FORUM - 20/03/2009 32

2,50 10
2,25 9
2,00
Start of XAA Autotrack 8 3sec
1,75 7
1,50 Offset 6
1,25 5
1,00 PT 4 XAA Autotrack
0,75 3
Tracking Errors (V)
Pointing Error (°)
0,50 2
0,25 1
0,00 0
-0,25 -1
-0,50 -2
-0,75 -3
-1,00 -4
-1,25 -5
-1,50 -6
-1,75 -7
-2,00 -8
-2,25 -9
-2,50 -10
-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Time (sec) Time (sec)
Azimuth Pointing Error Elevation Pointing Error Overall Pointing Error XAA Delta X XAA Delta Y
-10 10
9
-20 8
Start of 15m Autotrack 7
Signal Level at Tracking receiver Input (dBm)
-30 6
5 15m Autotrack
-40 4
3
Tracking Errors (V)
-50 2
1
-60 0
-1
-70 -2
-3
-80 -4
-5
-90 -6
3sec
-7
-100 -8
-9
-110 -10
-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Time (sec) Time (sec)
XAA AGC 15m AGC 15m Delta X 15m Delta Y
OPS-G FORUM - 20/03/2009 33

2,50 10
2,25 9
2,00
Start of XAA Autotrack 8
7
3sec
1,75
1,50 Offset 6
5
1,25
1,00 PT 4
0,75 3 XAA Autotrack
Tracking Errors (V)
Poinring Error (°)
0,50 2
0,25 1
0,00 0
-0,25 -1
-0,50 -2
-0,75 -3
-1,00 -4
-1,25 -5
-1,50 -6
-1,75 -7
-2,00 -8
-2,25 -9
-2,50 -10
-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Time (sec) Time (sec)
Azimuth Pointing Error Elevation Pointing Error Overall Pointing Error XAA Delta X XAA Delta Y
-10 10
9
-20 8
7
Signal level at Tracking receiver input (dBm)
-30 6
5
-40 4 15m Autotrack
3
Tracking Errors (V)
-50 2
1
-60 0
-1
-70 -2
Start of 15m Autotrack -3
-80 -4
-5
-90 -6
-7
2sec
-100 -8
-9
-110 -10
-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Time (sec) Time (sec)
XAA AGC 15m AGC 15m Delta X 15m Delta Y
OPS-G FORUM - 20/03/2009 34

• Herschel Plank LEOP support (April 2009)
• Factory Acceptance test of 2nd and 3rd XAA (June 2009)
• Installation and Site Acceptance in KRU (December 2009)
• Installation and Site Acceptance in MSP (June 2010)
• Lisa pathfinder LEOP support (March 2011)
OPS-G FORUM - 20/03/2009 35

• M. Arza & Perth M&O team (ONN)
• M. Lanucara, P. Droll, X. Enrich, A.Scior (GS)
• W. Hell (ONV)
• ERS2 & ENVISAT Flight Control Team
• M.A. Martin-Serrano & Flight Dynamic team
• K. Someya (JAXA)
OPS-G FORUM - 20/03/2009 36