Oliver's presentation about his Curiosity Clock application

1. Using Martian Data
Oliver Blake

2. Using Martian Data - Curiosity Clock
• The Curiosity Clock app
• Telling the time on Mars
• Building the Gale Crater
• Sunlight and shadows
• The Martian sky
• Viewing stars from Mars

3. The Curiosity Clock app
• Mars Science Laboratory (Curiosity Rover) landed in
the Gale Crater in August 2012
• Operations on Mars are dictated by the day/night
cycle, so calculations of time help with mission
planning
• Using the time algorithms, and in conjunction with
other available data, an Android app was created that
gives a virtual view as seen from the rover
• App features are...

4. The Curiosity Clock app
Sols (Martian days) Solar Time (and current
since landing displayed offset)
Position of
Sky colour the sun
Sunrise/set times Heading indicator Local terrain

5. Telling the time on Mars
• The time format used for Mars missions is based on the solar day -
a Martian day (or Sol) is 24.6 Earth hours long
• Local Mean Solar Time is a format where there are 24 hours in a
Sol, but each Mars hour is slightly longer to allow for the longer day
• Mars time calculations are based on the paper :
– “A post-Pathfinder evaluation of areocentric solar coordinates with improved timing
recipes for Mars seasonal/diurnal climate studies” by M Allison and M McEwen –
Planetary and Space Science 48 (2000)
• A series of numerical recipes contained within calculate the position
of Mars with relation to the sun for a given date, and with reference
to the landing information (time and location) for a particular Mars
lander, can be used to calculate the Sol number and solar time
• (Sol 0 is usually defined as starting at the local solar midnight on the
landing day)
• As part of the calculation the sun’s position relative to the landing
position is also worked out (more on this later)

6. Building the Gale Crater - Terrain
• The source data set – MOLA data from Mars Global
Surveyor (launched 1996)

7. Building the Gale Crater - Terrain
• MOLA data available for whole planet
• Different levels of detail available
– Lowest 4 pixels per degree – 4 * 2MB raw image files
– Highest 128 pixels per degree – 32 * 124MB files
• Need to balance level of detail with
processing requirements
• Image shows sub-set of data used for
Curiosity Clock app (brighter=higher)
• Raw image data and profile plotted with open
source ImageJ software (not to scale
vertically)
• In app, data is converted to a 3D polygon
terrain model

8. Building the Gale Crater - Detail
• After creating 3D terrain
model, image textures
can be added to give
more detail
• This image of the Gale
Crater was taken by an
orbiter (probably MGS
MOC) and tinted with a
generic Martian colour!

9. Comparison of app view with real view
• First panorama from Curiosity showing Mount
Sharp (Aug 2012), and recreation from Curiosity
Clock app

10. Sunlight and shadows
• The sunlight and shadows are more a programming task, but using data
from the first two sources
• The Mars time algorithm can also be used to calculate the azimuth and
elevation of the sun in the Martian sky
• A shadow map is created by checking for any points on the terrain where a
direct line to the sun intersects with another point on the terrain
• This images from the app show an aerial view of the Gale Crater, with
some shadowing visible from Mount Sharp, and a sun image with the size
adjusted accordingly for the increased distance compared to earth

11. The Martian sky
• There exist several sets of algorithms for calculating the sky colour
on Earth, taking into account the suns position in the sky and
atmospheric effects such as fog and haze.
• The basic effect is suitable for Mars – brighter as sun rises, bright in
direction of sun etc.
• Main difference is sky colour (usually referred to as butterscotch)
• Studies done of Mars sky 2006
colour using images from
Spirit and Opportunity Rovers
• Other difference from Earth
is blue sunsets (Spirit image)

12. Viewing stars from Mars
• Roughly half the time (depending on season) app is
used will be darkness – obvious answer to add interest
was to add some stars
• Bright Stars Catalogue lists brightest 9110 stars as seen
from Earth – position in sky, magnitude and colour
• Celestial sphere same for
Mars – although offset due VAUCOULEURS 1964
to different axial tilt – both
angle and direction (pole
stars etc. different)
• Drew the line at adding
moons, Phobos and
Deimos! (shapes, orbits etc)

13. 24 hours on Mars