Design Assessment of Lunar, Planetary and Satellite Ranging Applied to Fundamental Physics

Pioneer Anomaly Test – Jonathan Fitt

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Design Assessment of Lunar, Planetary and Satellite Ranging Applied to Fundamental Physics

Jonathan FittMonday, April 24, 2023

http://www.sr.bham.ac.uk/yr4pasr/project05/pioneer_anomaly/

A mission to test the Pioneer Anomaly




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Contents

• What are Lunar/Planetary/Satellite ranging?• Background to Pioneer Mission• Tracking the Pioneer craft• The Pioneer Anomaly• Exploring the Pioneer Anomaly• Direction & Summary


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Lunar Ranging

Lunar Ranging has been an experiment ongoing since the Apollo missions.

Pulses of laser light are sent to the moon and are reflected back by retro-reflectors left behind after landings.

The round trip light time (RTLT) of the pulse fundamentally defines the distance to the point on the moon.


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Planetary Ranging

Planetary ranging works on the same principle as Lunar Ranging but uses radio waves instead.

Radio waves are sent out from the Earth towards a planet and are either reflected back (Venus) or transponded back from a Lander (Mars).

The RTLT gives the distance information and the Doppler shift of the radio wave gives velocity information.


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Satellite Ranging

Earth orbiting satellites reflect laser light back down to Earth.

The LAGEOS mission uses passive retro-reflector satellites.

Active satellites can transmit their own signal and wait for it to be reflected off of the planet; Mars Global Surveyor.

The LAGEOS satellites provided valuable information about the structure and composition of the Earth.


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Satellite Ranging

Ranging does not have to be confined to craft orbiting planetary bodies.

Craft on interplanetary and outer solar system trajectories can also be tracked using ranging and Doppler methods.

Notable examples are Pioneer 10 & 11, the Voyager craft and Cassini.

Whilst the Pioneer craft were being tracked their Doppler information began to exhibit an un-modelled deceleration.


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Pioneer 10

Pioneer 10 was launched on 2nd March 1972 from Cape Canaveral. It was launched on board an Atlas/Centaur rocket.Pioneer 10 successfully encountered Jupiter on 4th December 1973


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Pioneer 10 & 11

In June 1983 Pioneer 10 was the first spacecraft to leave the solar system.

Pioneer 10 was also the first craft to enter the edge of interstellar space.

Pioneer 11 encountered Saturn and then left the solar system on a similar trajectory to Pioneer 10 but in the opposite direction


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Pioneer Orbits

20 A.U.

12.2 Km/s

’97

2000

67 A.U.75 A.U.

Modified from Anderson, J.D., et al., 2002, Phys. Rev. D 65


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Pioneer 10 – Layout

Anderson, J.D., et al., 2002, Phys. Rev. D 65


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Tracking The Pioneer Spacecraft

As the Pioneer craft got further into deep space the larger dishes of the Deep Space Network were needed to keep track of them

The DSN provided phase coherent tracking, telemetry and control (TT&C) at S-band


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Radio Science – Doppler Tracking

Doppler experiment: radio signal transmitted from the Earth to the spacecraft, coherently transponded and sent back to the Earth.

The frequency change of the received signal is measured with great accuracy.This is done over an integration time. And the craft is monitored over an observation time.

The observable is the received frequency.

The result is a ‘range rate’ of the spacecraft.

TfcvRf )1(


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Doppler Residual/Drift

caf

tff pobs 0mod DriftDoppler

2

f)( ResidualDoppler 20

mod

ctaf p

DSNobsff

For Pioneer 10 at S-band over 60s integration time.

Hzf 71070.7

210 )10168.8( msa p

19 )1099.5(Drift Doppler Hzs


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Doppler Velocity

The Doppler residual can be converted into a Doppler velocity

For S-band: 1 Hz = 68.2 mm/sTf

fc2

vlocity,Doppler ve D

Pioneer Anomaly Doppler velocity over 60s is 5.24x10-5 mm/s


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The Pioneer Anomaly

Beginning in 1987 and up until 1998 the Doppler data showed a constant residual deceleration in the range rate of the craft.

The Pioneer craft were tracked throughout their mission life.Doppler Velocity at S-band of Pioneer 10 between 1987 to 1998

-250

-200

-150

-100

-50

00 500 1000 1500 2000 2500 3000

Time (days)

Dopp

ler V

eloc

ity (m

m/s

)

Over this time Pioneer 10 moved 57 500 Km out of position.


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The Pioneer Anomaly

Actual plot of the data used to detect the Pioneer Anomaly between 1987 and 1998.

Anderson, J.D., et al., 2002, Phys. Rev. D 65


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A Mission to Test the Pioneer Anomaly

• The project is based on the proposal: A Mission to Explore the Pioneer Anomaly, http://arxiv.org/abs/gr-qc/0506139

• The proposal outlines key features needed for such a mission

• Verification of these features

http://arxiv.org/abs/gr-qc/0506139


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Key Mission Features

• Escape hyperbolic trajectory

• Trajectory stability of 10-10 ms-2

• Velocity different to Pioneer probes

• Reach 5 AU in a year

• Spin stabilized• Emitted radiation must be

symmetric, fore and aft• Communication X band,

possibly Ka band


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• Can these requirements be realised• What limits does the mission science place

on the craft• With these requirements will the Pioneer

Anomaly be tested

Spacecraft Requirements


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Pioneer Collaboration Proposal

•Spin stabilised•Passive retro-reflector test mass•Symmetric design•Radio ranging from the Earth to the mother craft•Laser ranging to the test mass from the mother craft•Remove common mode noise

Is this design to complicated?Can the required accuracy be achieved with current radio Doppler ranging?

A Mission to Explore the Pioneer Anomaly


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The Experiment

• The mother craft will follow the test mass at a distance of 1 Km

ydx

The Earth/proof mass range is unaffected by mother craft motion

Penanen and Chui, arxiv: gr-qc/0406013


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Current Project Work

Doppler Errors

Link Budget

Power Source

Mass/power budget


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Doppler Errors – jitter

To ensure that the observed Doppler velocity is due to the Pioneer Anomaly and not the Doppler jitter the craft needs to be tracked for a period of 2/5 of a day.

Doppler Velocity Residual at X-band

0.0023

0.0000

0.0005

0.0010

0.0015

0.0020

0.0025

0.0030

0.0035

0.0040

0.0045

0 0.01 0.02 0.03 0.04 0.05 0.06

Time (days)

Dopp

ler V

eloc

ity (m

m/s

)

ULNP

L

Lcv

c

BGTf

c)(

122

0

2


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Doppler Errors – Allan Deviation

Doppler Velocity Residual at X-band

0.0000

0.0002

0.0004

0.0006

0.0008

0.0010

0.0012

0.0014

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018

Time (days)

Dopp

ler V

eloc

ity (m

m/s

)

Anomaly Doppler Velocity (mm/s)Allan Error (mm/s)

Cy f

f

yv c

N

c yv

TN


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Link Budget – uplink

Ground to Space link

Parameter Value (linear) Value (dB)data rate (bps) 100 20range (m) 1.50E+13 131.76frequency up (Hz) 7.15E+09 98.54frequency down (Hz) 8.45E+09 99.27SNR (dB) 17

ConstantsPI 3.1416 4.97speed of light (m/s) 3.E+08 84.77k (W/Hz/K) 1.38E-23 -228.60

TransmittedEIRP (dBW) 96.00ponting loss (dB) -0.20atmospheric loss (dB) -0.15Receivedspreading loss (m -̂2) 4.44E-27 -263.52free space loss (m 2̂) 1.11639E-05 -49.52antenna gain (dB) 42.00amp gain (dB) 0.00antenna efficiency 0.6 -2.22Received Power (dBW) 1.67E-18 -177.76

Noise powersystem noise temp (K) 22 13.42specific thermal noise (W/Hz) 3.04E-22 -215.18system noise (W) 3.04E-20 -195.18receiver amp noise (dB) 0.00receiver noise (dB) -1.50total noise (dB) -196.68

System requirementreceived S/N (dB) 18.91

required S/N (dB) 17.00

link margin (dB) 1.91

Received power at the craft as a function of distance from the Earth

-190.00

-180.00

-170.00

-160.00

-150.00

-140.00

-130.00

-120.00

-110.00

-100.000 20 40 60 80 100 120 140 160

Distance (A.U.)

Rece

ived

Pow

er (d

BW)


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Link Budget – downlink

Power received at the ground station

-180.00

-170.00

-160.00

-150.00

-140.00

-130.00

-120.00

-110.00

-100.000 20 40 60 80 100 120 140 160

Distance (A.U.)

Rece

ived

Pow

er (d

BW)

Space to Ground link

Parameter Value (linear)Value (dB)data rate (bps) 100 20range (m) 1.50E+13 131.76frequency up (Hz) 7.15E+09 98.54frequency down (Hz) 8.45E+09 99.27SNR (dB) 17

ConstantsPI 3.1416 4.97speed of light (m/s) 3.E+08 84.77k (W/Hz/K) 1.38E-23 -228.60

TransmittedAntenna gain (dB) 15848.93 42.00antenna power (W) 1.60E-02 -17.96antenna efficeincy 0.6 -2.22EIRP (w) 1.52E+02 21.82

Receivedspreading loss (m -̂2) 4.44E-27 -263.52free space loss (m 2̂) 7.98E-06 -50.98amp gain (dB) 55.00

antenna gain (dB) 68pointing loss (dB) -0.40atmosphere loss (dB) -0.15Received Power (dBW) 9.49E-18 -170.23

Noise powersystem noise temp (K) 22 13.42specific thermal noise (W/Hz) 3.04E-22 -215.18system noise (W) 3.04E-20 -195.18

amp noise (dB) 0.00receiver noise (dB) 0.00total noise (dB) -195.18

System requirementreceived S/N (dB) 24.95

required S/N (dB) 17.00

link margin (dB) 7.95


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Power Source


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Mass/power budget

Mass/Power Budget

Power (w)Subsystem Component Mass (kg) Operation Total (W)TT&CScience Transponder 3 -12.9 -12.9

Antenna 10 0Laser 4.7 -16.8 -16.8Laser reciever 2 -10.8 -10.8Laser range unit 2 -10.8 -10.8

0Power 0

GPHS-RTG 55 290 290GPHS-RTG 55 290 290GPHS-RTG 55 290 290

Attitude 000000

Thermal 000000

Structure 0Test mass 20.6 0

0Fuel 0

000000

Total Mass (Kg) 207.3 Total Power (W) 818.7

Values taken from current work, design related to Doppler errors, link budget and power source

3 RTGs for symmetry about the spin axis

Max mass 300 Kg


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Future work

• Add to the power/mass budget for the Anomaly Test mission

• Work on the error budget for the Doppler radio link

• Create a design for the laser ranging link• Work on a laser link error budget• Design characteristics for the laser detector• Look into dimensions for the Test mission


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Summary

• Ranging techniques are used to test gravity theory

• The Pioneer Mission was simple yet effective

• Doppler tracking techniques are well developed

• Doppler velocity is crucial observable


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Summary

• Pioneer Anomaly deceleration is (8.74±1.33)x10-10 ms-2

• Characteristics for a mission to test the Anomaly – problem with velocity/range measurement integration

• Learn from the Pioneer Mission


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End

Any questions?


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Questions about the design

• High level of accuracy achievable with Doppler measurement of anomaly, 9.13x10-15 ms-2

• Earth/primary – Doppler measurement• Primary/test mass – range measurement• Radio ranging Earth/primary accurate to

0.95m


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Design Assessment of Lunar, Planetary and Satellite Ranging Applied to Fundamental Physics

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