Browsing by Subject "spacecraft"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Determining Nighttime Atmospheric Optical Depth Using Mars Exploration Rover Images(2013-07-22) Bean, Keri MarieMartian clouds and dust play an important part of the radiative transfer and energy balance budget. To assist in fully understanding the impact of clouds and dust, the complete diurnal cycle needs to be characterized. One of the best methods to track diurnal variations on Mars is by measuring optical depth. The spatial and temporal trends of optical depth give insight into the dust and water cycles of the Martian atmosphere. Until now, spacecraft could only obtain optical depth during the day. In this thesis, nighttime images from the Mars Exploration Rover Spirit are used to calculate nighttime optical depth using photometric methods to capture star flux. Bright stars in well-known constellations are used in this analysis. The observed flux was compared to the expected flux to give nighttime optical depth values. The observed nighttime optical depth was consistently similar to the daytime optical depth values on both an individual image and sol-averaged basis. Recommendations are made going forward to use the Mars Science Laboratory Curiosity for conducting an optimal nighttime optical depth campaign to fully characterize the diurnal dust and water cycles of Mars. The Curiosity rover is well suited for nighttime imaging and can potentially provide valuable insight into the nighttime dust and cloud trends.Item Small Satellite Applications of Commercial off the Shelf Radio Frequency Integrated Circuits(2012-02-14) Graves, JohnWithin the first decade of the 21st century, the aerospace community has seen many more opportunities to launch small spacecraft in the 10 to 100 kg mass class. Coupled with this has been consistent interest from the government in developing small-spacecraft platforms to expand civil and military mission possibilities. Small spacecraft have also given small organizations such as universities an increased access to space. Because small satellites are limited in size, power, and mass, new and often nontraditional capabilities must be explored and developed to make them viable and attractive when compared with larger and more proven spacecraft. Moreover, small organizations that wish to contribute technically are often limited by the small size of their teams and available resources, and need creative solutions for meeting mission requirements. A key need is in space-to-ground communications. Complex missions typically require large amounts of data transfer to the ground and in a timely fashion. Available options trade hardware cost, available ground stations or networks, available operating-frequency range, data-rate performance, and ease of use. A system for small spacecraft will be presented based upon Radio Frequency Integrated Circuits (RFIC) that minimizes development effort and maximizes interface control to meet typical small-spacecraft communications requirements. RFICs are low-cost components that feature pre-built radio hardware on a chip that can be expanded easily by developers with little or no radio experience. These devices are widespread in domestic applications for short-range connectivity. A preliminary design and prototype is presented that meets basic spaceflight requirements, offers data rates in the 55 to 85 kbps range, and has completed basic proof-of-concept testing. While there are higher-data-rate alternatives in existence, the solution presented here strikes a useful balance among data rate, parts cost, and ease of use for non experts, and gives the user operational control necessary to make air-to-ground communications time effective.