[Paper Review] Probing the Flyby Anomaly with the Galileo Constellation

Orfeu Bertolami, Frederico Francisco+2 more|arXiv (Cornell University)|Sep 13, 2011

Solar and Space Plasma Dynamics2 references3 citations

TL;DR

This paper proposes using the Galileo global navigation satellite system (GNSS) to detect and characterize the unexplained velocity changes in spacecraft during Earth flybys—known as the flyby anomaly—by leveraging multi-GNSS tracking of a dedicated micro-satellite mission. It demonstrates that offline processing and multi-constellation tracking could achieve the required ~1 mm/s velocity accuracy, making low-cost, high-precision monitoring of the anomaly feasible with existing or near-future GNSS infrastructure.

ABSTRACT

In the last few years, the so-called flyby anomaly has been widely discussed, but remains still an illusive topic. This is due to the harsh conditions experienced during an Earth flyby as well as due to the limited data available. In this work, we assess the possibility of confirming and characterizing this anomaly by resorting to the scientific capabilities of the future Galileo constellation.

Motivation & Objective

• To investigate whether the Galileo GNSS constellation can provide the necessary tracking accuracy to detect the flyby anomaly, which remains unexplained despite multiple deep-space flybys.
• To assess the feasibility of using existing or future GNSS systems for high-precision velocity tracking of spacecraft during Earth flybys, where the anomaly manifests as an unaccounted velocity shift.
• To propose a low-cost, dedicated micro-satellite mission with a highly elliptical orbit to enable repeated, controlled flyby-like maneuvers for improved anomaly characterization.
• To evaluate whether multi-GNSS tracking, especially offline processing and side-lobe techniques, can achieve the required ~1 mm/s velocity accuracy to detect the anomaly.
• To compare the scientific payoff of a dedicated mission versus adding a GNSS receiver to an existing mission with a highly elliptical orbit, favoring the former for better control and data quality.

Proposed method

• Utilizes offline processing of GNSS signals to improve tracking accuracy beyond real-time capabilities, targeting ~1 mm/s velocity precision.
• Proposes using multi-GNSS receivers (Galileo, GPS, etc.) to exploit diverse satellite geometries and enhance signal availability and tracking fidelity.
• Models the flyby anomaly as a velocity shift of ~10−4 m/s, consistent with observed discrepancies in Doppler and ranging data from past missions.
• Analyzes the potential of a micro-satellite in a highly elliptical orbit (HEO) or hyperbolic trajectory to mimic flyby conditions, with perigee velocities near 10 km/s.
• Suggests a spherical, spin-stabilized spacecraft design to minimize anisotropic effects and simplify modeling, enhancing data cleanliness.
• Compares the cost and feasibility of a dedicated mission (≤15M$) with a secondary payload approach, emphasizing cost efficiency and scientific return.

Experimental results

Research questions

• RQ1 Can multi-GNSS tracking with offline processing achieve the ~1 mm/s velocity accuracy required to detect the flyby anomaly?
• RQ2 What is the scientific advantage of a dedicated micro-satellite mission over adding a GNSS receiver to an existing HEO mission for flyby anomaly studies?
• RQ3 How do different error sources (e.g., atmospheric drag, solar pressure) compare in magnitude to the observed anomaly (~10−4 m/s²), and can they be ruled out?
• RQ4 To what extent can the flyby anomaly’s dependence on the asymptotic velocity vector’s declination be tested using GNSS data from a controlled, repeatable flyby-like trajectory?
• RQ5 Is the observed anomaly consistent with known physics, or does it point to new physical phenomena, and can GNSS-based tracking resolve this?

Key findings

• The flyby anomaly, observed in Galileo, NEAR, Rosetta, and Cassini flybys, manifests as an unexplained velocity change of ~3.9 mm/s (Galileo 1990) to ~13.5 mm/s (NEAR 1998), with a typical magnitude of ~10−4 m/s².
• Current real-time GNSS tracking is insufficient for detecting the anomaly, but offline processing and multi-GNSS tracking could achieve the required ~1 mm/s velocity accuracy.
• A dedicated micro-satellite mission with a mass <100 kg and budget ≤15M$ could provide high-precision, repeatable flyby-like conditions for anomaly characterization.
• The use of a spherical, spin-stabilized spacecraft design would minimize directional effects and improve modeling accuracy, enhancing data quality.
• The proposed method leverages existing Galileo and other GNSS constellations without requiring new space hardware, making it a cost-effective approach.
• The study concludes that there is no fundamental obstacle to using GNSS for flyby anomaly detection, and that such a mission offers a low-cost path to probing potential new physics.