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[edit] A Summary of Navigation and Guidance tasks associated with Project CLLARE

Abstract: This Technical Report provides a summary of navigation and guidance tasks associated with the CSTART Project CLLARE.

Contents 1 A Summary of Navigation and Guidance tasks associated with Project CLLARE 1.1 Introduction 1.2 Earth parking orbit determination 1.2.1 Sources of data 1.2.1.1 Onboard 1.2.1.2 Earth-based 1.2.2 Algorithms 1.3 Trans Lunar Injection timing 1.4 Trans lunar midcourse corrections 1.5 Lunar Orbit Insertion timing 1.6 Lunar orbit determination 1.7 Lunar descent 1.8 Lunar ascent 1.9 Lunar Orbit Rendezvous 1.10 Trans Earth injection timing 1.11 Trans earth midcourse corrections

[edit] Introduction

[edit] Earth parking orbit determination

The Falcon 9 (or other launch vehicle) places the CLLARE stack into a LEO parking orbit. The precise parameters of this orbit vary from launch to launch and so cannot be known in advance. The parameters must be determined as accurately as possible for the sake of accurately performing trans lunar injection.

[edit] Sources of data

[edit] Onboard

• Inertial navigation
• GPS
• Imaging of Earth surface?

[edit] Earth-based

• Visual observations (could crowdsource this?)
• Radiometric observations (distance and velocity)

[edit] Algorithms

• Gauss' algorithm
• Lambert's algorithm

[edit] Trans Lunar Injection timing

Once the parking orbit has been determined, it is possible to determine the best time to initiate and terminate the TLI burn. This cannot be accurately computed in advance to the uncertainty in parking orbit.

Probably best to compute ground-side using fast computers: numerically simulate trajectory for different initiation/termination times (searching the space in an intelligent manner) and find the most appropriate times. Simulation should take into account Earth atmosphere drag, gravity from Earth, moon and sun, solar wind pressure, etc. Possibly we can do an initial quick estimate using only gravity and then add perturbations one at a time?

[edit] Trans lunar midcourse corrections

[edit] Lunar Orbit Insertion timing

[edit] Lunar orbit determination

This is substantially more difficult than parking orbit determination - there's no GPS, no surface observations, etc. Need to research this more (e.g. how did Apollo do this?)

[edit] Lunar descent

[edit] Lunar ascent

This needs to be done much more carefully than lunar descent, in order to facilitate LOR.

An extremely simple ascent guidance approach was planned for the Apollo LESS, described here.

[edit] Lunar Orbit Rendezvous

[edit] Trans Earth injection timing

More or less the same procedure as TLI injection timing.

[edit] Trans earth midcourse corrections

It's vital to make sure the spacecraft encounters Earth's atmosphere inside the designated reentry corridor.