AIME For The Moon....And Beyond

Highlands Intermediate School
08-0012

Introduction

Landing

Design

Future

Bibliography

AIME's Design
     AIME has a box-like chassis constructed of aluminum to keep its weight down. A warm electronics box(WEB) houses and protects the computer, batteries, and electronic components. Above it is a rotating, triangular equipment deck on which is the MastCam mast assembly, antennas, and a camera calibration target. This design was inspired from the Mars Exploration Rovers, Spirit and Opportunity. [23]
     A Mast Camera takes the place of the PanCam of the M.E.R.s. The MastCam is a double camera system that can rotate on the mast and take panoramic shots of the lunar landscape and AIME as it explores the moon. It will provide color images, 3D stereo images, and HD color video. The videos will be taken at ten frames per second in HD allowing for smooth videos. The camera has a zoom of 10:1. The camera can take single exposure color shots and single color images, and can compress thousands of images and several hours of video.[13,14]
     Two mooncasts will be transmitted back to earth using a high gain, narrow beam directional dish antenna at a frequency of 10MHzRF in the X bandwidth. The antenna has a diameter of 0.55 meters and 683 transmitter elements, using only 12W of power. This antenna is on another mast, higher than the solar array. It will transmit at a high data rate and will be in HD to give near real time images. There is also an omnidirectional, low gain X band antenna to receive commands from Earth and to transmit to Earth should the high gain antenna fail. This antenna will only require 10W of power.[16] A UHF antenna will be used for communication with the orbiting spacecraft.[23] AIME will be autonomous, controlled by its computer and sensors but the low gain and UHF antenna enable Earth to periodically send commands if we find it necessary to reinvestigate an area or change direction.
     AIME has 2 arms attached to the front of the chassis. The instrument arm is equipped with the tools to search for minerals and water ice. The other arm is a grabbing arm that can pick up specimens and that can make adjustments to AIME if needed. The Rock Abrasion Tool (RAT) on the instrument arm will be used to remove dust and to grind rocks to reveal their undersurface for the spectrometers. This will help to search for traces of water ice and minerals on the moon. [4] A Hand Lens Imager that can focus on objects from one to ten inches away will record close up views of the rocks and soil to help determine minerals on the moon.[4,13]The Neutron Spectrometer will be used to look for water ice under the moon’s surface. By measuring neutrons excited by cosmic rays, it is possible to determine the amount of hydrogen present. The presence of hydrogen is indirect evidence of water ice.[8] The Alpha Particle X-Ray Spectrometer (APXS) mounted on the instrument arm will determine the elements in lunar rocks and soil by measuring the energy of alpha particles and x-rays beamed on them. This APXS may help find different minerals like silicon that could be mined on future missions.[4,12] An equipment called the Moessbauer Spectrometer will determine the presence and types of iron bearing minerals present on the lunar surface. [4]
     The solar array is 1.3 square meters in size and is mounted in a near vertical position since the sun’s path isn’t quite as high above the horizon near the South Pole.[9,21] It is mounted on the rotating equipment deck so that it can track and follow the sun’s path.
     AIME is powered by Triple Junction Gallium Arsenide cells (GaAs cells) and 4 lithium-ion batteries. GaAs cells have a high efficiency (25-30%), are able to withstand heat and radiation, and can be precisely controlled. Triple junction cells are made by stacking 3 layers of cells with the upper cells absorbing higher energy waves and the bottom cells absorbing lower energy waves, thereby increasing efficiency. [20, 21] The GaAs cells should be able to provide approximately 140W of steady power.[23]
     The M.E.R.s use about 100W of power for normal operations and 150W during transmission times.[19] The moon’s reduced gravity would require less power for AIME to run.[17] The M.E.R.s each weigh about 384 lbs. on Earth or 128 lbs. on Mars which has 1/3 of Earth’s gravity. They would weigh 64 lbs. on the Moon which has 1/6 of Earth’s gravity. AIME weighs less than 384 lbs. on Earth so it is less than 64 lbs. on the moon, and requires less energy to move. A solar array of the same size should absorb more energy on the moon since there is no atmosphere to block the sun’s rays, and less dust accumulation due to its near vertical tilt. AIME should have enough excess energy to run and to recharge its batteries for trips into the shadowed craters. [6, 15, 17]
     Lithium-ion batteries will be used on this mission because they are light, produce a high voltage, last long, generate less heat, and are rechargeable. The M.E.R.s use 2 lithium-ion batteries, but AIME will carry 4 to provide more backup power during its journeys into the dark craters and when it transmits its mooncasts. [19]
     There are six wheels, each powered by its own motor. The wheels are made out of aluminum and are about 26cm in diameter. There are cleats on each wheel to provide grip for climbing in soft sand and on rocks.   The wheels are filled with an open-cell foam called Solimide to keep dirt and rocks from ruining the drive and steering components. [24]
     The wheels are attached to a rocker-bogie suspension system that has joints that can rotate and that can adjust to the contour of the ground, allowing each wheel to move vertically independent of the other. This will enable AIME to go over rocky, uneven surfaces up to a tilt of 30^o without tipping over. [10, 23]
     AIME has 2 halogen headlights mounted on the front of the chassis & 1 halogen searchlight mounted on the MastCam assembly to enable the cameras to see when AIME travels into the dark craters and to take pictures.
     AIME has auto-navigational driving software to navigate. It can evaluate the terrain with stereo images taken by two stereo cameras, and then generate 3-D terrain maps of the area.   Next, using the height and density of rocks, excessive tilts, and the roughness of the terrain, it will determine a dozen possible paths then choose the safest one. AIME will then move between 0.5 to 2.0m towards its goal, continuously repeating this process until it reaches its goal. It will travel at an average speed of 34m/hour allowing it to cover 5000m in a little over six days of continuous sunlight on Malapert Mountain.[24] It is impossible to say exactly how far AIME will travel in its search for water ice. However, it will have 5 to 6 months of continuous sunlight on Malapert Mountain where it can return to recharge its batteries.
     A Visual Odometry software system will also help figure out where it is. It works by comparing pictures it took earlier with the ones it took after a short drive, automatically finding features in the terrain. Together with the 3-D terrain maps, it can figure out how and where the rover moves. [24]
     Aerogel is used for thermal insulation from the extreme temperatures on the moon. It can provide “thirty-nine times more insulation than the best fiberglass insulation” but “is 1,000 times less dense than glass”. [7]   Being 99.8% air, this will keep the rover’s weight down. [7]
     A thermostat will maintain a constant temperature. Radioisotope Heater Units (RHU) will keep the rover warm. The RHUs get their heat from the decay of Pu-238 and produce about 1W of heat each. They are tiny cylinders, the size of a spool of thread so their weight is minimal.[25] There is also a radiator to cool down the WEB when it gets too hot.[23]