Design Assessment of Lunar

Slide 1:Design Assessment of Lunar, Planetary and Satellite Ranging Applied to Fundamental Physics

Jonathan Fitt Wednesday, 22 December 2010 http://www.sr.bham.ac.uk/yr4pasr/project05/pioneer_anomaly/ A mission to test the Pioneer Anomaly

Slide 2:Contents

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

Slide 3: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. LLR has been used to test the Nordtvedt Effect to 7 parts in 1013 LLR has been used to test the Nordtvedt Effect to 7 parts in 1013

Slide 4: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. Planetary ranging tests warping of space time to 2 parts in 105 Also measures planetary ephemeris, for Mars accurate to 6mPlanetary ranging tests warping of space time to 2 parts in 105 Also measures planetary ephemeris, for Mars accurate to 6m

Slide 5: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. Satellite ranging used to gain knowledge of the Earth. Test for the Lense-Thirring Effect.Satellite ranging used to gain knowledge of the Earth. Test for the Lense-Thirring Effect.

Slide 6: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.

Slide 7: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

Slide 8: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

Slide 9: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 Orbits of the Pioneer craft, updated to show there current positions and velcoityOrbits of the Pioneer craft, updated to show there current positions and velcoity

Slide 10:Pioneer 10 � Layout

Anderson, J.D., et al., 2002, Phys. Rev. D 65 Schematic of the Pioneer craft, showing their simple yet effective symmetrical design about the spin axis (through the antenna).Schematic of the Pioneer craft, showing their simple yet effective symmetrical design about the spin axis (through the antenna).

Slide 11: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

Slide 12: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.

Slide 13:Doppler Residual/Drift

For Pioneer 10 at S-band over 60s integration time. The anomalous acceleration according to the data presented by Anderson et al. A Doppler residual is the difference between the modelled Doppler frequency and the actual received Doppler frequency. In an ideal situation the residual will always be equal to zero. But if forces are acting on the spacecraft causing it to change velocity then there will be a residual. It is this residual which leads to the anomalous acceleration.The anomalous acceleration according to the data presented by Anderson et al. A Doppler residual is the difference between the modelled Doppler frequency and the actual received Doppler frequency. In an ideal situation the residual will always be equal to zero. But if forces are acting on the spacecraft causing it to change velocity then there will be a residual. It is this residual which leads to the anomalous acceleration.

Slide 14:Doppler Velocity

The Doppler residual can be converted into a Doppler velocity For S-band: 1 Hz = 68.2 mm/s Pioneer Anomaly Doppler velocity over 60s is 5.24x10-5 mm/s The Doppler velocity measured on the original Pioneer data. Note that the new mission will use X-band.The Doppler velocity measured on the original Pioneer data. Note that the new mission will use X-band.

Slide 15: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. Over this time Pioneer 10 moved 57 500 Km out of position. The project has come up with a working model of how the Pioneer Anomaly was detected. This model can then be applied to the new mission in order to model the results and the craft.The project has come up with a working model of how the Pioneer Anomaly was detected. This model can then be applied to the new mission in order to model the results and the craft.

Slide 16: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 The actual data from the Pioneer 10. Note the remarkable comparison with the modelled data.The actual data from the Pioneer 10. Note the remarkable comparison with the modelled data.

Slide 17: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

Slide 18: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 These are the mission features which after studying the Pioneer Anomaly are essential for a future mission. The need for a symmetric design is so that any uncertainty to do with heat radiation pressure can be eliminated. One of the major debates is whether or not the heat being emitted from Pioneer 10�s RTGs is enough when reflected from the back of the antenna to cause the anomaly.These are the mission features which after studying the Pioneer Anomaly are essential for a future mission. The need for a symmetric design is so that any uncertainty to do with heat radiation pressure can be eliminated. One of the major debates is whether or not the heat being emitted from Pioneer 10�s RTGs is enough when reflected from the back of the antenna to cause the anomaly.

Slide 19: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

Slide 20: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 The mission features from the new proposal. Most are similar to that which we highlighted from investigating the anomaly. The need for laser ranging to the test mass is a feature of this particular design and the project work will verify it validity.The mission features from the new proposal. Most are similar to that which we highlighted from investigating the anomaly. The need for laser ranging to the test mass is a feature of this particular design and the project work will verify it validity.

Slide 21:The Experiment

The mother craft will follow the test mass at a distance of 1 Km The Earth/proof mass range is unaffected by mother craft motion Penanen and Chui, arxiv: gr-qc/0406013 Vector addition eliminates the common mode noise of the mother craft.Vector addition eliminates the common mode noise of the mother craft.

Slide 22:Current Project Work

Doppler Errors Link Budget Power Source Mass/power budget Along with verifying the claims made in the reporting of the Pioneer Anomaly. Verifying the aspects and features of the new proposal.Along with verifying the claims made in the reporting of the Pioneer Anomaly. Verifying the aspects and features of the new proposal.

Slide 23: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 jitter is an additive white Gaussian noise (AWGN).Doppler jitter is an additive white Gaussian noise (AWGN).

Slide 24:Doppler Errors � Allan Deviation

Allan variance is a measure of the stability of the oscillator against which the measurements are made.Allan variance is a measure of the stability of the oscillator against which the measurements are made.

Slide 25:Link Budget � uplink

SDST receiver threshold -156dBm which is -186dBW Start of mission distance 20 A.U. 100 A.U. is designed end of mission distanceSDST receiver threshold -156dBm which is -186dBW Start of mission distance 20 A.U. 100 A.U. is designed end of mission distance

Slide 26:Link Budget � downlink

Unknown receiver threshold for New Norcia NASA DSS in Canberra (DSS 43) detected Pioneer 10 with level of -208.5dBW in 2002 Start of mission distance 20 A.U. End of mission distance 100 A.U.Unknown receiver threshold for New Norcia NASA DSS in Canberra (DSS 43) detected Pioneer 10 with level of -208.5dBW in 2002 Start of mission distance 20 A.U. End of mission distance 100 A.U.

Slide 27:Power Source

General Purpose Heat Source � Radioisotope thermoelectric generator Can provide 290 Watts at start of life 5 year design life Weighs 55 Kg 3 to balance the craft: total power of 870 W Enough to provide power for the radio link at 16 W General Purpose Heat Source � Radioisotope thermoelectric generator Can provide 290 Watts at start of life 5 year design life Weighs 55 Kg 3 to balance the craft: total power of 870 W Enough to provide power for the radio link at 16 W

Slide 28:Mass/power budget

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 Mass/power budget containing the current preliminary design values. These are taken from non specific equipment but rather resemble the current technology being used to perfomr the same tasks as required by the design. The values for the laser equipment are drawn from no specific project work but form a rough target to aim for when the project work moves into designing the specifications for this equipment. The test mass is modelled on current satellites being used for laser ranging and the assumption that it will be no larger 1.5 m in diameter.Mass/power budget containing the current preliminary design values. These are taken from non specific equipment but rather resemble the current technology being used to perfomr the same tasks as required by the design. The values for the laser equipment are drawn from no specific project work but form a rough target to aim for when the project work moves into designing the specifications for this equipment. The test mass is modelled on current satellites being used for laser ranging and the assumption that it will be no larger 1.5 m in diameter.

Slide 29: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 Add mass/power for the attitude control system and the thermal control system Add solar corona noise to the error values for the Doppler radio link Come up with components suitable for laser ranging Generate the error budget for the laser ranging stage of the experiment Physical dimensions for the equipment/spacecraft. What is its size?Add mass/power for the attitude control system and the thermal control system Add solar corona noise to the error values for the Doppler radio link Come up with components suitable for laser ranging Generate the error budget for the laser ranging stage of the experiment Physical dimensions for the equipment/spacecraft. What is its size?

Slide 30: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 Doppler techniques have been used to perform many modern precise measurements of physical constants. LLR, SLR and planetary ranging have all used laser/Doppler techniques effectively therefore these can be applied to a mission to test the Pioneer Anomaly. The Doppler velocity is essential in determining any anomalous accelerationDoppler techniques have been used to perform many modern precise measurements of physical constants. LLR, SLR and planetary ranging have all used laser/Doppler techniques effectively therefore these can be applied to a mission to test the Pioneer Anomaly. The Doppler velocity is essential in determining any anomalous acceleration

Slide 31: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 The Pioneer Mission was highly successful and provided good results in measuring the anomaly. Therefore any new mission will have to draw heavily from the original Pioneer craft and the work done in analysing the data from these.The Pioneer Mission was highly successful and provided good results in measuring the anomaly. Therefore any new mission will have to draw heavily from the original Pioneer craft and the work done in analysing the data from these.

Slide 32:End

Any questions?

Slide 33: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

Slide 34:Blank