RAMSES Mission Analysis 
Ruaraidh Mackenzie, Ignacio Acedo, Davide Basso
The Rapid Apophis Mission for Space Safety (RAMSES) forms part of the European Space Agency's (ESA) Space Safety Programme and is dedicated to the study of asteroid Apophis. Although preparatory activities commenced in 2024, the mission received formal approval during the ESA ministerial meeting in November 2025.
The primary objective of RAMSES is to conduct comprehensive surveys of Apophis’s surface, shape, orbital parameters, and orientation both prior to, during, and following its Earth flyby in April 2029. ESA’s Ramses spacecraft will rendezvous with Apophis ahead of its close approach to Earth, accompanying the asteroid during the flyby to observe and record any changes induced by the planet’s gravitational influence.
Driven by the imperative to arrive in advance of the predetermined flyby event, the mission implements accelerated development strategies, maximising reuse of the Hera platform. RAMSES is being executed in collaboration with JAXA, utilising an H3 launcher shared with the Destiny+ mission. Launch is scheduled for April 2028, with injection targets coordinated between ESA and JAXA. The ten-month interplanetary cruise culminates in arrival at Apophis in February 2029, affording a short two-month window for rendezvous and initial asteroid characterisation prior to the Earth encounter.
A major challenge to ground operations is the rendezvous phase, which requires a delta-v of approximately 1.5 km/s, delivered through a sequence of five manoeuvres over a 14-day period, thereby reducing relative velocity for transition into asteroid characterisation. This phase includes 3 further manoeuvres in 12 days, positioning the spacecraft within a series of hyperbolic arcs approximately 10 km from Apophis.
Following the initial characterisation, navigation responsibility transitions from ground-based control to on-board autonomous control. This publication details the mission analysis undertaken to ensure the safe navigation of the spacecraft, including launcher evaluation, interplanetary cruise, rendezvous and transfer to close asteroid characterisation, for delivery to the on-board autonomous GNC control. 
The paper will describe the challenge of a shared launcher; implementing a robust rendezvous phase, accounting for possible failures in the manoeuvre sequence; and an optimal transfer to the asteroid characterisation orbit.