# The flyby anomaly: A multivariate analysis approach

## TL;DR

This paper investigates the flyby anomaly, an unexpected velocity change during spacecraft Earth flybys, using a multivariate analysis to suggest it may be caused by a hypothetical fifth force with a specific range.

## Contribution

It introduces a multivariate dimensional analysis approach to model the flyby anomaly and proposes the existence of a fifth force with a range of about 300 km as a potential explanation.

## Key findings

- Estimated the fifth force range around 300 km
- Identified local parameters at perigee as key factors
- Provided a new phenomenological fitting model

## Abstract

The flyby anomaly is the unexpected variation of the asymptotic post-encounter velocity of a spacecraft with respect to the pre-encounter velocity as it performs a slingshot manoeuvre. This effect has been detected in, at least, six flybys of the Earth but it has not appeared in other recent flybys. In order to find a pattern in these, apparently contradictory, data several phenomenological formulas have been proposed but all have failed to predict a new result in agreement with the observations. In this paper we use a multivariate dimensional analysis approach to propose a fitting of the data in terms of the local parameters at perigee, as it would occur if this anomaly comes from an unknown fifth force with latitude dependence. Under this assumption, we estimate the range of this force around 300 km.