Pioneer Anomaly Test – Jonathan Fitt 1 Design Assessment of Lunar, Planetary and Satellite Ranging Applied to Fundamental Physics Jonathan Fitt Friday, 16 October t05/pioneer_anomaly/ A mission to test the Pioneer Anomaly

Pioneer Anomaly Test – Jonathan Fitt 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

Pioneer Anomaly Test – Jonathan Fitt 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.

Pioneer Anomaly Test – Jonathan Fitt 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.

Pioneer Anomaly Test – Jonathan Fitt 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.

Pioneer Anomaly Test – Jonathan Fitt 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.

Pioneer Anomaly Test – Jonathan Fitt 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

Pioneer Anomaly Test – Jonathan Fitt 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

Pioneer Anomaly Test – Jonathan Fitt 9 Pioneer Orbits 20 A.U Km/s ’ A.U. 75 A.U. Modified from Anderson, J.D., et al., 2002, Phys. Rev. D 65

Pioneer Anomaly Test – Jonathan Fitt 10 Pioneer 10 – Layout Anderson, J.D., et al., 2002, Phys. Rev. D 65

Pioneer Anomaly Test – Jonathan Fitt 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

Pioneer Anomaly Test – Jonathan Fitt 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.

Pioneer Anomaly Test – Jonathan Fitt 13 Doppler Residual/Drift For Pioneer 10 at S-band over 60s integration time.

Pioneer Anomaly Test – Jonathan Fitt 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

Pioneer Anomaly Test – Jonathan Fitt 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 Km out of position.

Pioneer Anomaly Test – Jonathan Fitt 16 The Pioneer Anomaly Actual plot of the data used to detect the Pioneer Anomaly between 1987 and Anderson, J.D., et al., 2002, Phys. Rev. D 65

Pioneer Anomaly Test – Jonathan Fitt 17 A Mission to Test the Pioneer Anomaly The project is based on the proposal: A Mission to Explore the Pioneer Anomaly, The proposal outlines key features needed for such a mission Verification of these features

Pioneer Anomaly Test – Jonathan Fitt 18 Key Mission Features Escape hyperbolic trajectory Trajectory stability of 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

Pioneer Anomaly Test – Jonathan Fitt 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

Pioneer Anomaly Test – Jonathan Fitt 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

Pioneer Anomaly Test – Jonathan Fitt 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/

Pioneer Anomaly Test – Jonathan Fitt 22 Current Project Work Doppler Errors Link Budget Power Source Mass/power budget

Pioneer Anomaly Test – Jonathan Fitt 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.

Pioneer Anomaly Test – Jonathan Fitt 24 Doppler Errors – Allan Deviation

Pioneer Anomaly Test – Jonathan Fitt 25 Link Budget – uplink

Pioneer Anomaly Test – Jonathan Fitt 26 Link Budget – downlink

Pioneer Anomaly Test – Jonathan Fitt 27 Power Source

Pioneer Anomaly Test – Jonathan Fitt 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

Pioneer Anomaly Test – Jonathan Fitt 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

Pioneer Anomaly Test – Jonathan Fitt 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

Pioneer Anomaly Test – Jonathan Fitt 31 Summary Pioneer Anomaly deceleration is (8.74±1.33)x ms -2 Characteristics for a mission to test the Anomaly – problem with velocity/range measurement integration Learn from the Pioneer Mission

Pioneer Anomaly Test – Jonathan Fitt 32 End Any questions?

Pioneer Anomaly Test – Jonathan Fitt 33 Questions about the design High level of accuracy achievable with Doppler measurement of anomaly, 9.13x ms -2 Earth/primary – Doppler measurement Primary/test mass – range measurement Radio ranging Earth/primary accurate to 0.95m

Pioneer Anomaly Test – Jonathan Fitt 34 Blank