20 research outputs found
433 Eros Landing – Development of NEAR Shoemaker’s Controlled Descent Sequence
On February 12th, 2001, the NEAR Shoemaker spacecraft made its historic descent to the surface of the asteroid 433 Eros, becoming the first spacecraft to soft land on a small celestial body. Development of the final descent activity offered the NEAR team a difficult technical challenge as the spacecraft had been designed solely as a free flyer, not as a lander. The NEAR Shoemaker spacecraft rendezvoused with 433 Eros on February 14th, 2000. Following an intensive year of orbital operations collecting science data at decreasingly lower altitudes, the spacecraft was prepared to conduct its final activity, descending from its current 36 km orbit in a series of five propulsive maneuvers to land on the surface of 433 Eros. As a free flyer, the spacecraft’s orbital operations were extremely successful, collecting an order of magnitude more images of the asteroid’s surface than originally planned. However, since the spacecraft was not designed to be a lander, landing presented a whole new challenge to the Navigation, Mission Design, Guidance and Control, and Mission Operations Teams. This paper discusses the development of the controlled descent sequence from an operations perspective, focusing on the inherent difficulties of performing an activity for which the spacecraft was not originally designed, and the way in which these challenges were overcome by the NEAR team
Unattended network operations technology assessment study. Technical support for defining advanced satellite systems concepts
The results are summarized of an unattended network operations technology assessment study for the Space Exploration Initiative (SEI). The scope of the work included: (1) identified possible enhancements due to the proposed Mars communications network; (2) identified network operations on Mars; (3) performed a technology assessment of possible supporting technologies based on current and future approaches to network operations; and (4) developed a plan for the testing and development of these technologies. The most important results obtained are as follows: (1) addition of a third Mars Relay Satellite (MRS) and MRS cross link capabilities will enhance the network's fault tolerance capabilities through improved connectivity; (2) network functions can be divided into the six basic ISO network functional groups; (3) distributed artificial intelligence technologies will augment more traditional network management technologies to form the technological infrastructure of a virtually unattended network; and (4) a great effort is required to bring the current network technology levels for manned space communications up to the level needed for an automated fault tolerance Mars communications network
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Atmospheric observations made at Oliktok Point, Alaska, as part of the Profiling at Oliktok Point to Enhance YOPP Experiments (POPEYE) campaign
Between 1 July and 30 September 2018, small unmanned aircraft systems (sUAS), tethered balloon systems (TBSs), and additional radiosondes were deployed at Oliktok Point, Alaska, to measure the atmosphere in support of the second special observing period for the Year of Polar Prediction (YOPP). These measurements, collected as part of the Profiling at Oliktok Point to Enhance YOPP Experiments (POPEYE) campaign, targeted quantities related to enhancing our understanding of boundary layer structure, cloud and aerosol properties and surface–atmosphere exchange and providing extra information for model evaluation and improvement work. Over the 3-month campaign, a total of 59 DataHawk2 sUAS flights, 52 TBS flights, and 238 radiosonde launches were completed as part of POPEYE. The data from these coordinated activities provide a comprehensive three-dimensional data set of the atmospheric state (air temperature, humidity, pressure, and wind), surface skin temperature, aerosol properties, and cloud microphysical information over Oliktok Point. These data sets have been checked for quality and submitted to the US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program data archive (http://www.archive.arm.gov/discovery/, last access: July 2019) and are accessible at no cost by all registered users. The primary dataset DOIs are https://doi.org/10.5439/1418259 (DataHawk2 measurements; Atmospheric Radiation Measurement Program, 2016), https://doi.org/10.5439/1426242 (TBS measurements; Atmospheric Radiation Measurement Program, 2017) and https://doi.org/10.5439/1021460 (radiosonde measurements; Atmospheric Radiation Measurement Program, 2013a).</p