Bussey, Ben - New Analyses of the Moon’s North Polar Illumination Conditions

Abstract: 
We continue to enhance our LunarShader illumination simulation capability. This tool accurately determines the surface illumination conditions given a topography file and a selected date/time. Recent improvements include

We have analyzed the Moon’s north polar region using LunarShader and recent high-resolutions Digital Elevation Models. We have determined which sites receive the most illumination and then for those sites we fully characterize the illumination conditions. This analysis includes deriving several parameters of interest when planning either a lunar lander or rover mission.  Examples of such parameters include:-

1. Longest single period of continuous illumination
2. Longest single period of constant shadow
3. Mean amount of illumination
4. Areas receiving no illumination (permanently shadowed)
5. Earth-visibility maps

Each of these parameters is useful for different types of mission…

1. Regions which have the longest single period of constant illumination, centered on mid-summer, are of interest for lander missions that want as long a duration as possible but are not designed to survive a lunar night. Analyses of the polar regions have revealed that locations exist that are continuously illuminated for several months.

2. For extremely long surface missions, i.e. multiple years, a key parameter is the longest single period of constant shadow. This can determine the battery mass that is required to provide enough energy to heat key components. If the lander can survive the longest shadow it should be able to survive the whole year, so long as there is enough time to recharge once the longest shadow period ends before the next period begins.

3. The mean amount of illumination simply shows the percentage of time that a point on the surface is illuminated.  We have known for sometime that places exist that are illuminated for over 70% of the time during a winter day and 100% of a summer day. Often this type of study is undertaken to identify which locations to do detailed illumination studies on.

4. Areas that receive no illumination, i.e. are permanently shadowed are known to be extremely cold and can harbor volatile deposits. Analysis of LOLA topography revealed that permanent shadow can exist at latitudes as low as 58°.

5. LunarShader can also determine whether a location can see the Earth at a particular time. This is key information for either a lander or rover that will use Direct To Earth (DTE) communications rather than a relay communication satellite. sAdditionally we have developed to ability to determine when a lander is in line of sight of a deployed rover. This is useful for the mission scenario where the rover requires a lander for high data rate communications with Earth.