- An advanced tool for LEOP support -

OPS-G FORUM 20/03/2009

2OPS-G FORUM - 20/03/2009

PART1 - Overview of requirement and Technical implementationPiermario 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 validationFilippo Concaro: OPS-GSA

– On-site installation– Alignment– Site Acceptance tests– XAA system tests

3OPS-G FORUM - 20/03/2009

•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.

4OPS-G FORUM - 20/03/2009

LISA Pathfinder (Rockot launcher) 3σ dispersion from Perth

-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

-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

Cross-Elevation Pointing Error

Elev

atio

n po

intin

g Er

ror

Within 15m tracking range (8.1%)

Within XAA Tracking Range (99.8%)

Outside XAA tracking range (0.2%)

•New missions will not use S-band (2 GHz), but X-Band (8 GHz) for LEOP.

•The beam in X-band is 4 times smaller than S-Band

•The tracking range of the ESTRACK 15m antennas is too small to cover the foreseen dispersion area

•The actual 15m antenna search function is too slow to cope with the spacecraft’s speed during LEOP

(In order to cover this latter cases one could use the search function with the XAA antenna)

5OPS-G FORUM - 20/03/2009

• 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)

6OPS-G FORUM - 20/03/2009

Not compliant in terms of maximum time required to acquire (Worst case: 40 sec)

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

7OPS-G FORUM - 20/03/2009

• 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

8OPS-G FORUM - 20/03/2009

• 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 reflectors2. Optimised Corrugated feed-horn3. Wave guide feeding system4. Very low noise amplifiers5. Compact outdoor down converter6. Temperature controlled outdoor box7. Last generation Tracking Receiver

9OPS-G FORUM - 20/03/2009

10OPS-G FORUM - 20/03/2009

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

-16

17

8

EL error [mdeg] 0 -4 -32

TOT error [mdeg] 0 6 33

XAA Pointing errors wrt Antenna Elevation

Elevation 0° 30° 60° 90°

AZ error [mdeg] 0/3 0/1 0/0

14/15

14/15

0/0

EL error [mdeg] 27/30 24/26 0/-3

TOT error [mdeg] 27/30 24/26 0/3

15m Pointing errors wrt Antenna Elevation w/o and with XAA

11OPS-G FORUM - 20/03/2009

Sun-Shield

XAA LNAs Thermal analysis

XAA DC Thermal analysis

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

12OPS-G FORUM - 20/03/2009

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

13OPS-G FORUM - 20/03/2009

14OPS-G FORUM - 20/03/2009

Supporting structure Antenna

Outdoor Equipment box Counterweights

15OPS-G FORUM - 20/03/2009

Correct XAA-15m antennas alignment is crucial

1. Mechanical alignment2. RF alignment

(Calibration tower)3. RF alignment verification

on spacecraft

Specified alignment accuracy is 30 mdeg

Alignment procedure consists of 3 steps:

16OPS-G FORUM - 20/03/2009

Rough alignment at 90° Elevation

Fine alignment at 0° Elevation

17OPS-G FORUM - 20/03/2009

D = 4400 m

θ = 0.110°

θ = atan(L/D)

-30,0

-20,0

-10,0

0,0

10,0

20,0

30,0

40,0

50,0

60,0

70,0

-0,400 -0,300 -0,200 -0,100 0,000 0,100 0,200 0,300 0,400

Offset from Boresight direction (deg)

Ant

enna

Gai

n (d

Bi)

XAA SUM XAA DELTA 15m DELTA 15m SUM

The distance between the XAA and the 15m antenna electrical centres (L) is not negligible with respect to the antenna – Calibration tower distance (D), this results in an angular offset (θ), which has to be taken into account for the RF alignment and the acceptance tests

θ

L = 8.5 m

Alignment goal:0.110°±0.03° offset in Azimuth0 ° ±0.03° offset in Elevation

18OPS-G FORUM - 20/03/2009

• Measurement on calibration tower are affected by several factors:

1. Deformation of antenna mechanical structure due to gravity

2. Multipath and fading effects due to ground reflections

15 meter antenna null position on Calibration Tower “moves” with frequency and polarisation

PER1 15m antenna - X-Band Tracking Null Positions on Calibration Tower

0,7400,7500,7600,7700,7800,7900,8000,8100,8200,8300,8400,8500,8600,8700,8800,890

202,860202,870202,880202,890202,900202,910202,920202,930202,940202,950202,960202,970202,980202,990203,000203,010203,020203,030203,040203,050203,060203,070203,080

Azimuth (deg)

Elev

atio

n (d

eg)

RHC LHC

Plank Herschel

Lisa PF RHC Lisa PF LHC

(Measurement accuracy ~10 mdeg)

XAA-15m RF alignment on Calibration Tower is frequency dependant

19OPS-G FORUM - 20/03/2009

RF Alignment on Calibration Tower is optimised for Lisa Pathfinder (8495 MHz) frequency RHC polarisation

20OPS-G FORUM - 20/03/2009

Perth X-Band 15m and XAA Tracking (Delta) Null and Sum pattern Peak positions

0,7000,7100,7200,7300,7400,7500,7600,7700,7800,7900,8000,8100,8200,8300,8400,8500,8600,8700,8800,8900,9000,9100,920

202,85202,86202,87202,88202,89202,90202,91202,92202,93202,94202,95202,96202,97202,98202,99203,00203,01203,02203,03203,04203,05203,06203,07203,08203,09203,10

Azimuth (deg)

Elev

atio

n (d

eg)

15m SUM RHC

15m DELTA RHC

15m SUM LHC

15m DELTA LHC

XAA SUM RHC NF

XAA DELTA RHC NF

XAA SUM LHC NF

XAA DELTA LHC NF

XAA SUM RHC FF

XAA DELTA RHC FF

XAA SUM LHC FF

XAA DELTA LHC FF

15m antenna tracking range

The enlarged points are the ones for 8495 MHz (Lisa Pathfinder) RHC

RF RF Alignment on Calibration Tower for LPF frequency, RHCAlignment on Calibration Tower for LPF frequency, RHC

Measurement Accuracy is:±5 mdeg for 15m delta null and sum peak±15 mdeg for XAA delta null±30 mdeg for XAA sum peak

21OPS-G FORUM - 20/03/2009

Perth X-Band 15m and XAA Tracking (Delta) Null and Sum pattern Peak positions

0,7000,7100,7200,7300,7400,7500,7600,7700,7800,7900,8000,8100,8200,8300,8400,8500,8600,8700,8800,8900,9000,9100,920

202,85202,86202,87202,88202,89202,90202,91202,92202,93202,94202,95202,96202,97202,98202,99203,00203,01203,02203,03203,04203,05203,06203,07203,08203,09203,10

Azimuth (deg)

Elev

atio

n (d

eg)

15m SUM RHC

15m DELTA RHC

15m SUM LHC

15m DELTA LHC

XAA SUM RHC NF

XAA DELTA RHC NF

XAA SUM LHC NFXAA DELTA LHC NF

XAA SUM RHC FF

XAA DELTA RHC FF

XAA SUM LHC FF

XAA DELTA LHC FF

15m antenna tracking range

The enlarged points are the ones for 8495 MHz (Lisa Pathfinder) LHC

Even if affected by the mentioned disturbance factors, the graph shows that also for LHC polarisation the XAA tracking null position corrected by the Far Field (FF) –Near Field (NF) offset falls within the 15m antenna tracking range.

RF RF Alignment on Calibration Tower for LPF frequency, LHCAlignment on Calibration Tower for LPF frequency, LHC

Measurement Accuracy is:±5 mdeg for 15m delta null and sum peak±15 mdeg for XAA delta null±30 mdeg for XAA sum peak

22OPS-G FORUM - 20/03/2009

-30,0

-20,0

-10,0

0,0

10,0

20,0

30,0

40,0

50,0

60,0

70,0

-0,400 -0,300 -0,200 -0,100 0,000 0,100 0,200 0,300 0,400

Offset from Boresight direction (deg)

Ant

enna

Gai

n (d

Bi)

XAA SUM XAA DELTA 15m DELTA 15m SUM

D >> L

θ = 0°

In the case of a spacecraft, the distance between the XAA 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

23OPS-G FORUM - 20/03/2009

Spacecraft GEOTAIL ERS2 ENVISAT

Agency JAXA ESA

8040/1840

Cross Correlation

Fast

Flux at antenna(including Modulation Loss) <-163 dBW/m2 >-133 dBW/m2 >-131 dBW/m2

1 or 2 times/day

ESA

Frequency [MHz] 8474.66 8200/8300

Tracking Mode PLL Cross Correlation

Spacecraft Speed Slow Fast

Availability 1 day/week at perigee 1 or 2 times/day

24OPS-G FORUM - 20/03/2009

GEOTAIL Autotrack XAA-15m comparison for a 40° Elevation Pass & 120.000 km range

-0,200

-0,150

-0,100

-0,050

0,000

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)

Elev

atio

n Po

intin

g Er

ror (

deg)

XAA Average Null (with STDEV)15m Average Null (with STDEV)15m NULLXAA NULL

High dispersion due to very low signal

Offset magnitude is consistent with what observed on the Calibration Tower

25OPS-G FORUM - 20/03/2009

XAA-DC

XAA-TRR

XAASUM & DELTA

Channel Selection

TRR

LDCSUM & DELTA

Channel Selection FEC

ELXEL

ELXEL

EL

ELEL

ELXEL

XELXEL

XEL

AGC

AGC

SwitchM&C

Switch M&C

Test Signal

AZEL

XAAAntenna

PER1Antenna

Spacecraft

Frequency

EL, XEL, AGC, Lock, PLL BW, TR Mode

EL, XEL, AGC, Lock, PLL BW, TR ModeFrequency

Switch M&C

Switch M&CAZ, EL

PLOTTERor

DATALOGGER

XDCMIXER

TEST SYNTHESIZER

Frequency

SMC

XAA-SMC

AGC

AGC

ACU

Both ERS2 and Envisat are using X-band to dump data at high data rate.

The frequency used are:8040 and 8140 MHz for ERS28200 and 8300 MHz for ENVISAT

While XAA Downconverter covers the band between 8025 to 8500 MHz, the 15m antenna Downconverters covers only the Space Research band (8400-8500 MHz)

an additional converter (mixer) had to be used to translate the frequency in the required range

TEST SETUP

26OPS-G FORUM - 20/03/2009

ENVISAT Autotrack XAA-15m comparison for a 55° MAX Elevation Pass

-0,200

-0,150

-0,100

-0,050

0,000

0,050

0,100

0,150

0,200

-0,200 -0,150 -0,100 -0,050 0,000 0,050 0,100 0,150 0,200Cross-elevation Pointing Error (deg)

Elev

atio

n Po

intin

g Er

ror (

deg)

XAA Average Null (with STDEV)15m Average Null (with STDEV)15m NULLXAA NULLProgram Track

Smaller dispersion due to much higher signal (like expected in a LEOP scenario)

Offset magnitude is consistent with what observed on GEOTAIL and on the Calibration Tower

27OPS-G FORUM - 20/03/2009

• G/T• Tracking range & tracking slope• Acquisition range

28OPS-G FORUM - 20/03/2009

XAA G/T at 5 and 30 deg Elevation

10,0

11,0

12,0

13,0

14,0

15,0

16,0

17,0

18,0

19,0

20,0

8000 8100 8200 8300 8400 8500

Frequency [MHz]

dB/K

RHC - LNA1 - 5 deg LHC - LNA2 - 5 degRHC - LNA1 - 30 deg LHC - LNA2 - 30 deg

Specification

29OPS-G FORUM - 20/03/2009

XAA Tracking Sensitivity8495 MHz LHC (Lisa Pathfinder)

-10,00

-9,00

-8,00

-7,00

-6,00

-5,00

-4,00

-3,00

-2,00

-1,00

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

8,00

9,00

10,00

-1,50 -1,00 -0,50 0,00 0,50 1,00 1,50

Boresight Azimuth offset (°)

Trac

king

Err

or V

olta

ges

(V)

DELTA X DELTA Y

•The graphs shows the linearity of the tracking errors wrt angular offset at 8495 MHz.

•Due to the fact that the antenna beam gets narrower as the frequency increases, it can be considered as a worst case scenario.

•In the specified range of ±1°the red curve is pretty much linear and the cross talk (blue curve) negligible

•The tracking range extends up to roughly ±1.2°

30OPS-G FORUM - 20/03/2009

XAA Tracking Sensitivity8495 MHz LHC (Lisa Pathfinder)

-10,00

-9,00

-8,00

-7,00

-6,00

-5,00

-4,00

-3,00

-2,00

-1,00

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

8,00

9,00

10,00

-1,50 -1,00 -0,50 0,00 0,50 1,00 1,50

Boresight Azimuth offset (°)

Trac

king

Err

or V

olta

ges

(V)

DELTA X DELTA Y

XAA Tracking Sensitivity8495 MHz RHC (Lisa Pathfinder)

-10,00

-9,00

-8,00

-7,00

-6,00

-5,00

-4,00

-3,00

-2,00

-1,00

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

8,00

9,00

10,00

-1,50 -1,00 -0,50 0,00 0,50 1,00 1,50

Boresight Azimuth offset (°)

Trac

king

Err

or V

olta

ges

(V)

DELTA X DELTA Y

XAA Tracking Sensitivity8495 MHz LHC (Lisa Pathfinder)

-10,00

-9,00

-8,00

-7,00

-6,00

-5,00

-4,00

-3,00

-2,00

-1,00

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

8,00

9,00

10,00

-1,50 -1,00 -0,50 0,00 0,50 1,00 1,50

Boresight Elevation offset (°)

Trac

king

Err

or V

olta

ges

(V)

DELTA X DELTA Y

XAA Tracking Sensitivity8495 MHz RHC (Lisa Pathfinder)

-10,00

-9,00

-8,00

-7,00

-6,00

-5,00

-4,00

-3,00

-2,00

-1,00

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

8,00

9,00

10,00

-1,50 -1,00 -0,50 0,00 0,50 1,00 1,50

Boresight Elevation offset (°)

Trac

king

Err

or V

olta

ges

(V)

DELTA X DELTA Y

The graphs below show the measured tracking slopes for different polarisations and axis

31OPS-G FORUM - 20/03/2009

PLL bandwidth (Hz) 3000 1000 300 100

Acquisition range (°) >±0.5 >±1 >±1.25 >±1.4

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

Tests on GEOTAIL•Marginal Power Flux Density•Offsets wrt nominal trajectory obtained applying time offset to the program track

Tests on ERS2/ENVISAT•Suppressed carrier mode•Offsets wrt nominal trajectory obtained using ad-hoc modified STDMs

32OPS-G FORUM - 20/03/2009

• 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 secTime 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)

33OPS-G FORUM - 20/03/2009

-10-9-8-7-6-5-4-3-2-10123456789

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

Time (sec)

Trac

king

Err

ors

(V)

15m Delta X 15m Delta Y

-2,50-2,25-2,00-1,75-1,50-1,25-1,00-0,75-0,50-0,250,000,250,500,751,001,251,501,752,002,252,50

-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)

Poin

ting

Erro

r (°)

Azimuth Pointing Error Elevation Pointing Error Overall Pointing Error

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-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

Time (sec)

Sign

al L

evel

at T

rack

ing

rece

iver

Inpu

t (dB

m)

XAA AGC 15m AGC

-10-9-8-7-6-5-4-3-2-10123456789

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

Time (sec)

Trac

king

Err

ors

(V)

XAA Delta X XAA Delta Y

Start of XAA AutotrackOffset

PT

3sec

XAA Autotrack

Start of 15m Autotrack

3sec

15m Autotrack

34OPS-G FORUM - 20/03/2009

-10-9-8-7-6-5-4-3-2-10123456789

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

Time (sec)

Trac

king

Err

ors

(V)

15m Delta X 15m Delta Y

-10-9-8-7-6-5-4-3-2-10123456789

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

Time (sec)

Trac

king

Err

ors

(V)

XAA Delta X XAA Delta Y

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-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

Time (sec)

Sign

al le

vel a

t Tra

ckin

g re

ceiv

er in

put (

dBm

)

XAA AGC 15m AGC

-2,50-2,25-2,00-1,75-1,50-1,25-1,00-0,75-0,50-0,250,000,250,500,751,001,251,501,752,002,252,50

-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)

Poin

ring

Erro

r (°)

Azimuth Pointing Error Elevation Pointing Error Overall Pointing Error

Start of XAA AutotrackOffset

PT

3sec

XAA Autotrack

Start of 15m Autotrack

2sec

15m Autotrack

35OPS-G FORUM - 20/03/2009

• 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)

36OPS-G FORUM - 20/03/2009

• 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)