First published Spring 2012, Crosslink® magazine.
Aerospace Supports New Weather Satellite
The National Polar-Orbiting Operational Environmental Satellite System Preparatory Project (NPP), a new NASA weather satellite, launched from Vandenberg Air Force Base on a Delta II rocket October 28, 2011. The satellite, precursor to the Joint Polar Satellite System, is equipped with sensors that will observe the ozone layer, atmospheric temperatures, and Earth’s changes. Data from the satellite should offer scientists information to help them monitor long-term climate patterns and also help meteorologists more accurately predict weather.
“Aerospace supported the specification, development, and performance of three sensors flying on the satellite from cradle to launch,” said Patricia Maloney, associate principal director, Earth and Science Climate Directorate. “Aerospace also led the mission system integration and test campaign, and provided instrument flight management for activation and commissioning of the sensors,” said Maloney.
The three sensors include a visible infrared imager radiometer suite that will observe broad areas of land, ocean, and air offering information about everything from polar ice caps to minute ocean life. Another sensor will study infrared radiance, supporting improvements to global weather forecasts and helping scientists better predict and understand severe weather shifts. An ozone mapper and profiler suite will measure ozone level distribution in the atmosphere at higher resolutions than have previous instruments.
NPP provides data continuity with NOAA 19, the last of the National Polar-Orbiting Operational Environmental Satellite System program satellites, and will observe the afternoon orbit over Earth. The afternoon observations complement those from other weather satellites in early morning and midmorning orbits.
Curiosity on a Mission to Mars
NASA’s Mars Science Laboratory rover, Curiosity, launched aboard an Atlas V from Cape Canaveral November 26, 2011, beginning its two-year mission to Mars. Aerospace provided systems engineering and mission assurance support to the development team during the last five years. This work included selective reliability studies, resolving issues with many of the complex mechanisms on the rover, and supporting the certification for flight readiness process.
“The rover’s mission is to study the geology of Mars, and from it infer the natural processes involving water that shaped its history,” said Roy Nakagawa, systems director, Planetary and Robotic Missions. “The rover is a mobile geology lab, with a suite of laboratory-quality instruments for sampling and determining the composition of rock samples that the rover will collect during its surface mission. The mission will help determine whether Mars has the ability to support microbial life,” said Nakagawa.
Curiosity is the fourth rover to travel to Mars. It carries ten science instruments, and has six aluminum wheels, a pair of cameras, an articulating arm, and a laser that can determine the elemental composition of rocks and soil. The rover is larger than those that came before it (Sojourner, Spirit, and still active Opportunity), and cannot be sustained by airbags for landing. The plan is for Curiosity to land inside Mars’s Gale Crater using a sky crane touchdown in tandem with a rocket-powered descent lowering it on tethers. The rover is scheduled to reach the crater in August 2012.
Ultrasonic Testing Finds New Application
Aerospace has developed a nondestructive ultrasonic method to test preload measurements of separation bolts while a launch vehicle is on a launchpad by injecting sound pulses into the bolt at its head. The time required for return of an echo of the pulse from the bolt end can then be measured. This new application of ultrasonic testing saves Aerospace customers time and money by avoiding launch delays. “Aerospace developed this technique because of a test failure in a new lot of separation nut assemblies where there was possible improper preload. For proper function, the separation bolt preload needs to be within specification,” said Eric Johnson, Space Materials Laboratory. The procedure was applied to launch vehicles at Cape Canaveral and Vandenberg Air Force Base. The Cape vehicle tested fine, but the results for Vandenberg indicated that the bolt preloads were significantly below minimum requirements. “The paperwork revealed that the prelubricated bolts had been removed and reinstalled during a prior operation, rather than replaced. The reuse of bolts increased friction between the bolt and the nut, thus reducing the preload upon installation,” said Johnson. The launch vehicle contractor decided to remove and replace the separation nut assemblies. New ones were shipped to the launch facility and, using the same ultrasonic method, Aerospace verified the preloads prior to further processing.
Aerospace Has a New Vacuum Chamber
A new space-simulation vacuum chamber built to carry out electrostatic discharge testing arrived at The Aerospace Corporation in November 2011. The chamber, called ESD1, will examine electrostatic discharges caused by interactions between a spacecraft and charged particles in space.
Electrostatic discharge can damage spacecraft components and lead to operational anomalies. ESD1 will help with the investigation of scale-up effects, charge-flow dynamics, and electromagnetic interference, as well as assist in finding better ways to perform electrostatic discharge testing. ESD1 will also be used for testing of solar array designs and anomaly resolution.
“Having this chamber will allow Aerospace to conduct more research and improve the quality and quantity of work in the electrostatic discharge area. The chamber does a good job of simulating the space environment and testing various kinds of space hardware,” said Mark Crofton, senior scientist, Electric Propulsion and Plasma Science.
ESD1’s inside surface finish is unusual. It is mechanically polished, which reduces the effective surface area and outgassing rates. This helps to lower the pressure inside the chamber, which is vital for simulating the space environment. ESD1 is 17 feet long, with a diameter of 8.5 feet, and weighs 14,000 pounds. The stainless steel vessel will be a critical tool for evaluating and improving space power system designs.
GRAIL Begins Lunar Orbit
The Gravity Recovery and Interior Laboratory has begun orbiting the moon. Launched on a Delta II September 10, 2011, the twin satellites, which were built by NASA, reached orbit on December 31, 2011, and January 1, 2012.
“Aerospace provided technical support to JPL on the GRAIL mission through system level reliability analyses that helped mission planners make decisions on the redundancy of elements required to ensure mission success. The onboard instruments are delicate, and Aerospace was asked to perform a coupled loads analysis that led to the selection of a vibration isolation system to protect the payload during launch,” said Roy Nakagawa, systems director, Planetary and Robotic Missions. The solar-powered satellites will use gravitational field mapping to study the interior structure of the moon. Orbiting 34 miles above the moon’s surface, in polar orbits, radio-ranging instruments on GRAIL-A and GRAIL-B will precisely measure the intersatellite spacing. Variations in that spacing will be sent back to Earth and processed to determine the moon’s gravitational field and its interior structure.
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