5
Mission Operations
The Icebreaker robot has several modes of operation. Which mode the robot is in at a particular time is based on the visibility of the Sun and Earth. Changes in Sun and Earth visibility cause the robot to switch between modes.
The modes considered are Launch/Landing, initial test/shakedown, driving, drilling/scientific analysis, charging and hibernation. The modes are explained in detail below.
	5.1	Launch/Landing Operations
The Icebreaker will launch on a Delta II 7925H rocket from the Kennedy Space Center. The spacecraft will travel to the Moon on a direct descent trajectory, and will only require one trajectory correction maneuver during transit. DSN will be used to track the spacecraft during transit.
A star tracker camera, IMU, and the DSN will establish the vehicle position, orientation and velocities during the initial descent. Approximately 50km above the surface, initial deceleration will commence using a solid rocket motor.
Final deceleration phase will commence with the dropping of the solid rocket motor after its burn is complete. A camera and radar altimeter, on the belly of the robot, will be used during final descent to further establish vehicle position, orientation and velocity in conjunction with DSN, star tracker, and IMU. Final descent will be controlled with Main Thrust system of 12 34lbf hydrazine thrusters pointing down, and the Attitude Control System consisting of smaller thrusters to control attitude of vehicle as well as remove spin.
Besides being used to help determine vehicle position during landing the belly camera will be used to take pictures of the areas surrounding the landing site for future planning information. It will also be used to select a precise landing spot which will then be visually servoed to during the descent.
Landing will occur with almost zero energy eliminating the need for large shock absorbing materials. Furthermore, the hydrazine propulsion systems will not be dropped but carried with the robot. The rational behind this choice is that the propulsion system is not significant in mass, compared to the rover, and any excess fuel remaining could be used in an emergency situation to lift the rover out of a crater or other hazard.
	5.2	Lunar Surface Operations
The modes other than landing can be considered to be lunar surface operations since they take place on the lunar surface. They are discussed in detail in this section, but first we need to define some terms which describe the state of the Sun and Earth visibility.
The environment of the lunar south pole region presents several conditions which the robot must deal with during the mission duration. The conditions considered in this document can be divided into lighting conditions and communications availability. They are:
Lighting Conditions
•	Lunar Night - Sun is below the horizon for long period of time
•	Lunar Day - Sun visible
•	Shadow - darkness caused by terrain blocking the Sun
•	Cold Trap Darkness - darkness caused by cold traps rather than the Sun setting
Communications Availability
•	Earthnight - Earth is below Moon’s horizon for long period of time.
•	Earthshadow - Earth is temporarily obscured by terrain blocking line of sight
•	Earthday - Earth is visible, communications are available
•	Cold Trap Earthshadow - purposefully entering a cold trap from which communications are not possible
	5.2.1	Initial Test Mode/Shakedown
This mode is performed immediately after landing. The purpose of it is to allow mission control to determine the health of all major subsystems. The robot will return data (provided the comm system is functional) on its internal status such as temperature, battery status, solar panel output and estimated position. Camera views of the surrounding will also be returned, providing useful information to the operator about the area. Short drives will be undertaken, and the drill will perform some test drills.
It is assumed that a priori information can guarantee that this mode occurs during the lunar day with full communications (Earthday).
	5.2.2	Driving
The driving mode is when the Icebreaker is in motion. During Earthday (when communications are possible) the driving will be done using a form of waypoint control by an operator on Earth. The robot will use its two forward looking cameras to capture a stereo image. This image will be sent back to Earth where an operator, wearing 3D goggles will identify a set of way points designating a path for the robot to follow. This path will be returned to the robot which will then follow the path, and then send back a new image. The robot remains stationary from the time the stereo image is captured to the time it receives the path from the operator. Image transmission requires 25 seconds. The robot will endeavor to use this time to partially charge its batteries. While the robot is driving, other data, such as panospheric images or internal sensor values can be returned, however the driving is done with the stereo image. In between waypoints, driving is completely autonomous, and the robot is capable of avoiding obstacles such as boulders and chasms by itself using radar sensors. If a designated way point is inside an object the robot will get as close as possible and then wait for further commands from Earth. A typical sequence of robot/operator interactions is shown in Table 1.1.
This mode assumes that we have Earthday and Lunar Day conditions. Shadow can be distinguished from Lunar Night (which is very predictable), and most likely can be driven through under battery power. Earthnight will cause the robot to transition to Charging or Hibernation modes
	TABLE  1.1	.Robot/Operator Interactions
Icebreaker	Ground Based Operator	
Send images from forward cameras		
Send telemetry	See Rover’s eye view in 3-D	
Wait for “GO”	Select waypoints	
	Give science instructions if necessary	
	Can request other images/telemetry	
	Give Icebreaker a “GO” signal	
Traverse waypoints, safeguarded	Monitor progress/telemetry	
Arrive at Goal waypoint		
The likelihood of entering an Earthshadow is high since the Earth is very low on the horizon. While the robot is driving between way points Earth comm is not required and the robot will proceed through its waypoints. If the robot is within Earthshadow when it reaches the last waypoint, it will continue driving in the same direction (avoiding obstacles) for a fixed distance. If communications are still not present, the robot will then use its stored path, and using its tracks as a visual cue, drive back to the last spot where communications existed.
Entering and exiting cold traps is a somewhat special case of driving. The mission will endeavor to find a cold trap which has Earthday. Upon entering such a cold trap, driving will commence using the waypoint control as before, however lights or strobes will be used as necessary to augment the illumination provide by Earthshine. Unfortunately it is not possible at this time to guarantee that a cold trap with Earthday will exist. This uncertainty means that the robot must be capable of autonomously entering, analyzing, and exiting a cold trap under the Cold Trap Shadow conditions. The robot will do this using its terrain radar units to avoid obstacles. Using the panospheric camera to identify the horizon, it can calculate when an area will be permanently shadowed. It should be noted that this mode of operation will only be used as a last resort if cold traps with Earthday cannot be located, or if ice was not found in any of these traps.
	5.2.3	Drilling/Scientific Analysis
Scientific analysis will occur primarily inside cold traps. Once inside a cold trap, the robot will use a sensor to remotely detect volatiles (this sensor is as yet undetermined). If no volatiles are visible, the robot will execute a search grid inside the cold trap using the remote ice sensor to look for volatiles. The robot, and human operator, will be aware of battery status and allow sufficient time for the robot to exit the cold trap, before the batteries become critically low. Once ice is detected, the robot will position the drill and begin taking samples. Samples will be taken from the ice using the drill. These samples will be transported from the drill to an evolved gas analyzer (EGA). The EGA will then determine the composition of the sample. Up to ten samples will be taken from the same bore hole at different depths.
Due to the risks involved with entering and exiting a cold trap, the robot will do the analysis of all samples in the cold trap. The number of samples taken inside the cold trap will also be maximized. However, due to the limited power available from batteries, the robot may be required to enter and exit the cold trap multiple times to charge batteries.
The scientific analysis will, by its very nature, be done under Cold Trap Darkness lighting conditions. The communications conditions are much less well defined. Ideally a cold trap with ice will be found under Earthday conditions. However, by the very nature of cold traps the horizon will be higher than normal (to block out the Sun), it is expected that Earthshadows will be more common than while in the light. The distinct possibility exists that all cold traps, with ice, will be in Cold Trap Earthshadow which would require completely autonomous operations of the robot. These cold traps will only be explored as a last resort. 
	5.2.4	Charging
The design of the Icebreaker robot consists of a fixed vertical solar panel which runs from the bow to the stern of the robot. This solar fin has charging surfaces on both sides. However, it is not pointable, so it is conceivable that at times the robot will be driving off its battery reserves even while it is in Lunar Day conditions. Another load on the battery arises from cold trap operations. It is expected that a cold trap sortie will last for 10 hours on average. This will use almost half of the battery capacity.
Since it will not be possible to keep the batteries fully charged during driving and it is desirable to have fully charged batteries before entering a cold trap, the robot will stop and charge at times, most likely just before entering a cold trap and just after exiting a cold trap. To do this Icebreaker will stop with its solar fin perpendicular to the Sun for maximum power generation. While charging it may be possible to return images and data of its surrounding, depending on power availability.
Charging must be performed in Lunar Day conditions. While Earthday is not strictly necessary, it is advantageous so that the operator realizes what is occurring. This mode of operation may also occur during the conjuncture of Lunar Day condition with Earthnight, since the robot is not expected to carry on operations during the long (approx. 14 days) period during which the Earth is below the horizon due to its orbit and not terrain.
	5.2.5	Hibernation
Hibernation is a state during which operations are halted and power consumption is reduced to the minimum possible values. No communications, scientific analysis, driving, or imagery is performed.
This mode of operations is entered when Lunar Night falls. Since the Sun is no longer visible the robot must survive on batteries alone. This fall of Lunar Night should not be confused with Shadows or Cold Trap darkness. Lunar Night is something which can be predicted by operators on Earth and so can be distinguished from Shadow which is darkness caused by driving behind a hill or rock. Cold Trap darkness is simply a form of shadow, which by searching the angles to the horizon (with the panospheric camera) can be determined to be permanent.