Master's Thesis

The work on my master's thesis is ongoing; the deadline is set to March 12, 2012. Once the thesis have been reviewed and my final oral exam is over, the thesis will be published as book in spring 2012. In addition, the digital version of this book will be available here as e-book for download free of charge (the book is published under a free license).

Until this point of time this page is used for a sneak preview of the thesis contents and results. This page is subject to change over time.

General Information

Thesis Type	Master's Thesis
Major	Computer Science and Communication Systems/Artificial Intelligence
Academic Degree	Master of Engineering (M.Eng.)
Title	Development of an illumination simulation software for the Moon's surface: An approach to illumination direction estimation on pictures of planetary solid surfaces with a significant number of craters.
Supervisors	German Aerospace Center (DLR) Institute of Space Systems, Bremen Dipl. Math.-Techn. Bolko Maass	Merseburg University of Applied Sciences Department of Computer Science and Communication Systems Prof. Dr. rer. nat. Hartmut Kröner

Thesis Background and Contents (Abstract)

The exploration of the solar system over the last decades broadened our knowledge and understanding of the universe and our place in it. Great scientific and technological achievements have been made, allowing us to study faraway places in the solar system. The world's space agencies are now facing a new era of continuing space exploration in the 21st century, expanding permanent human presence beyond low Earth orbit for the first time. Pursuing this goal, the development of advanced technologies urges more than ever before.

One key technology for future human and robotic missions to distant places from Earth will be the ability of an autonomous navigation and landing of spacecraft, since nowadays navigation systems rely on Earth based navigation techniques (tracking, trajectory modeling, commanding). A promising approach are optical navigation technologies, which can operate completely independent from Earth, allowing a surface-relative navigation and landing on celestial bodies without human intervention.

The German Aerospace Center (DLR) is developing a new, holistic optical navigation system for all stages of an approach and landing procedure within the ATON project (Autonomous Terrain based Optical Navigation). Central point of this new navigation system is the landmark based navigation. Commonly, craters are used as landmarks, as they exhibit very characteristic shapes and they are long-time steady in shape, struture and positioning. However, the flawless perception of those surface features by computers is a non-trivial task.

A new edge-free, scale-, pose- and illumination-invariant crater detection algorithm is developed for ATON, which will cut away incisive limitations of current algorithms. To push on further development, a possibility to generate realistic surface images with well-known illumination conditions as well as a technique for the estimation of the illumination direction on those pictures is essential. To date, an applicable software for the generation of artificial renderings of realistically illuminated planetary surfaces while determinating the illumination direction is missing.

Said this, the objective of this thesis was the development of a surface illumination simulation sofware for planetary solid surfaces with a significant amount of craters, whereas all work has been done in the context of the Moon. The thesis work lead to the development of the Moon Surface Illumination Simulation Framework (MSISF), which is able to produce realistic renderings of the entire lunar surface while altering illumination conditions. It maintains a global digital elevation model of the Moon, using latest data sets from the ongoing NASA Lunar Reconnaissance Orbiter (LRO) mission.

With the MSISF, a basis for the further development of the new crater detection algorithm as well as the illumination direction estimation on pictures of planetary solid surfaces has been established.

Previews

Video: Copernicus crater during sundown

In this video you can observe the Copernicus crater on the Moon's surface during sundown. The simulation starts at 2011/12/15 00.00.00 UTC and will end on 2011/12/20 00.00.00 UTC.

Background Information:
The movie consists out of 501 single renderings in intervals of approx. 14 minutes, generated with my simulation software ("Moon Surface Illumination Simulation Framework", MSISF) and composed as a video sequence.

The MSISF maintains a database of so-called "surface patterns". Those surface patterns are slices of the Moon's surface, which have been preprocessed as 3D meshes (spatial points connected as triangles). Those patterns are currently available with spatial resolutions of 4, 16 and 64 pixels per degree (longitude/latitude), which refers to approximately 7.581, 1.895 and 0.474 km per pixel at the equator, respectively. The topography data is based on the Lunar Orbiter Laser Altimeter (LOLA) instrument data sets of the ongoing NASA Lunar Reconnaissance Orbiter (LRO) mission. Simply put, the MSISF selects the needed surface patterns accordingly to the visible surface for each picture, does the necessary (astro-)dynamical calculations (i.e. for the Sun, Moon and spacecraft positions), initiates the rendering of the scene and does some postprocessing with the final rendering. The rendering itself is done by POV-Ray, which is integrated in the MSISF.

Some words on the complexity:
All calculations and renderings are done on a single standard machine in 25 hours. The MSISF pattern repository is 125 GiB large, consisting of 265 million vertices for the highest resolution of 64 pixels per degree. Notwithstanding that resolutions till 1024 pixels per degree (corresponds to 29.6 m/pixel) are currently available from NASA LRO LOLA, 64 pixels per degree is pretty much the limit for computability on standard personal computers (my system configuration: Intel Core2 Quad Q6600 4x 2.4 GHz, 16 GB G.Skill RAM DDR2-800).

Local Solar Illumination Angle Determination