Engineering topics
Ravine, M. A.
Publications and source records attributed to Ravine, M. A..
The Mars Science Laboratory Curiosity Rover Mastcam Instruments: Preflight and In-Flight Calibration, Validation, and Data Archiving
The NASA Curiosity rover Mast Camera (Mastcam) system is a pair of fixed-focal length, multispectral, color CCD imagers mounted approximately 2 m above the surface on the rover's remote sensing mast, along with associated electronics and an onboard calibration target. The left Mastcam (M-34) has a 34 mm focal length, an instantaneous field of view (IFOV) of 0.22 mrad, and a FOV of 20 deg × 15 deg over the full 1648 × 1200 pixel span of its Kodak KAI-2020 CCD. The right Mastcam (M-100) has a 100 mm focal length, an IFOV of 0.074 mrad, and a FOV of 6.8 deg × 5.1 deg using the same detector. The cameras are separated by 24.2 cm on the mast, allowing stereo images to be obtained at the resolution of the M-34 camera. Each camera has an eight-position filter wheel, enabling it to take Bayer pattern red, green, and blue (RGB) 'true color' images, multispectral images in nine additional bands spanning approximately 400-1100 nm, and images of the Sun in two colors through neutral density-coated filters. An associated Digital Electronics Assembly provides command and data interfaces to the rover, 8 Gb of image storage per camera, 11 bit to 8 bit companding, JPEG compression, and acquisition of high-definition video. Here we describe the preflight and in-flight calibration of Mastcam images, the ways that they are being archived in the NASA Planetary Data System, and the ways that calibration refinements are being developed as the investigation progresses on Mars. We also provide some examples of data sets and analyses that help to validate the accuracy and precision of the calibration.
Mars Hand Lens Imager (MAHLI) efforts and observations at the “Rocknest” Eolian sand shadow in Curiosity’s Gale Crater field site
The Mars Science Laboratory (MSL) mission is focused on assessing the past or present habitability of Mars, through interrogation of environment and environmental records at the Curiosity rover field site in Gale crater. The MSL team has two methods available to collect, process and deliver samples to onboard analytical laboratories, the Chemistry and Mineralogy instrument (CheMin) and the Sample Analysis at Mars (SAM) instrument suite. One approach obtains samples by drilling into a rock, the other uses a scoop to collect loose regolith fines.
Mars Observer camera
The Mars Observer camera (MOC) is a three-component system (one narrow-angle and two wide-angle cameras) designed to take high spatial resolution pictures of the surface of Mars and to obtain lower spatial resolution, synoptic coverage of the planet's surface and atmosphere. The cameras are based on the 'push broom' technique; that is, they do not take 'frames' but rather build pictures, one line at a time, as the spacecraft moves around the planet in its orbit. MOC is primarily a telescope for taking extremely high resolution pictures of selected locations on Mars. Using the narrow-angle camera, areas ranging from 2.8 km x 2.8 km to 2.8 km x 25.2 km (depending on available internal digital buffer memory) can be photographed at about 1.4 m/pixel. Additionally, lower-resolution pictures (to a lowest resolution of about 11 m/pixel) can be acquired by pixel averaging; these images can be much longer, ranging up to 2.8 x 500 km at 11 m/pixel. High-resolution data will be used to study sediments and sedimentary processes, polar processes and deposits, volcanism, and other geologic/geomorphic processes.
An analysis of morphologic variation in simple lunar craters
Previous photogeologic classification of lunar craters have differentiated them into various morphologic types. In an attempt to identify the physical factors responsible for these morphologic variations, this study examined 44 fresh, simple lunar craters between 1.1 and 14 km in diameter on the maria. Photogeologic analysis was performed using Apollo stereo panoramic photography, while a quantitative analysis of cross-sectional shape was done using Fourier analysis. These analyses showed that the sample could not be split into two distinct types (flat- and round-floored) as had been done previously. The two crater types at best represent end-members of a distribution of morphologies. Some correlation was found between the degree of relative degradation and floor roundness, implying that flat floors are primary and round floors are degradational features. No difference was found between the average depth-to-diameter ratio of flat- and round-floored craters, indicating that the factor of two variation in depth-to-diameter ratio in this sample of fresh craters is a primary morphologic feature and that minor degradation of fresh craters has no significant effect on average crater depth.