Commissioning the Webb telescope to realize the observatory’s full capability necessitated the development of robust wavefront sensing and control processes. These processes rely on techniques that were adapted or newly innovated for the mission, and further adaptation of these techniques may be expected for future segmented telescopes. Over the course of mission development, these techniques were refined to form a baseline wavefront commissioning plan that assumes several conditions and performance requirements are met. Herein we present efforts carried out to define and develop contingency concepts of operation for Webb telescope commissioning, and the mission-level approach to managing the response to deviations from the baseline plan in the event of significant off-nominal or anomaly scenarios encountered by the wavefront team. An overview of selected contingencies is presented along with more detailed example model cases and instances of interest encountered in flight.
GEOScan is a proposed space-based facility of globally networked instruments that will provide revolutionary, massively dense global geosciences observations. Major scientific research projects are typically conducted using two approaches: community facilities, and investigator lead focused missions. While science from space is almost exclusively conducted within the mission model, GEOScan is a new concept designed as a constellation facility from space utilizing a suite of space-based sensors that optimizes the scientific value across the greatest number of scientific disciplines in the earth and geosciences, while constraining cost and accommodation related parameters. Our grassroots design processes target questions that have not, and will not be answered until simultaneous global measurements are made. The relatively small size, mass, and power of the GEOScan instruments make them an ideal candidate for a hosted payload aboard a global constellation of communication satellites, such as the Iridium NEXT's 66-satellite constellation. This paper will focus on the design and planning components of this new type of heterogeneous, multi-node facility concept, such as: costing, design for manufacture, science synergy, and operations of this non-traditional mission concept. We will demonstrate that this mission design concept has distinct advantages over traditional monolithic satellite missions for a number of scientific measurement priorities and data products due to the constellation configuration, scaled manufacturing and facility model.
GEOScan is a grassroots effort, proposed as globally networked orbiting observation facility utilizing the main Iridium NEXT 66-satellite constellation. This will create a revolutionary new capability of massively dense, global geoscience observations and targets elusive questions that scientists have not previously been able to answer, and will not answer, until simultaneous global measurements are made. This effort is enabled by Iridium as part of its Hosted Payload Program. By developing a common sensor suite the logistical and cost barriers for transmitting massive amounts of data from 66 satellites configured in 6 orbital planes with 11 evenly spaced slots per plane is removed. Each sensor suite of GEOScan’s networked orbital observation facility consists of 6 system sensors: a Radiometer to measure Earth’s total outgoing radiation; a GPS Compact Total Electron Content Sensor to image Earth’s plasma environment and gravity field; a MicroCam Multispectral Imager to measure global cloud cover, vegetation, land use, and bright aurora, and also take the first uniform instantaneous image of the Earth; a Radiation Belt Mapping System (dosimeters) to measure energetic electron and proton distributions; a Compact Earth Observing Spectrometer to measure aerosolatmospheric composition and vegetation; and MEMS Accelerometers to deduce non-conservative forces aiding gravity and neutral drag studies. Our analysis shows that the instrument suites evaluated in a constellation configuration onboard the Iridium NEXT satellites are poised to provide major breakthroughs in Earth and geospace science. GEOScan commercial-of-the-shelf instruments provide low-cost space situational awareness and intelligence, surveillance, and reconnaissance opportunities.
New horizons is a NASA sponsored mission to explore Pluto and its largest moon Charon. The new horizons spacecraft, designed, built and operated by the Johns Hopkins University Applied Physics Laboratory (APL), was successfully launched in January 2006 and will perform its primary mission at Pluto in the summer of 2015. To support this mission, the spacecraft is equipped with onboard software that provides a rule based expert system for performing autonomous fault detection and recovery. This system has been updated nine times since launch and is continuously being tested to ascertain its performance in various spacecraft states. The test approach for the autonomous fault protection subsystem is to perform a combination of unit-level tests and full system scenario tests. For the scenario tests, we have developed a "lights out" test method and have been using it to reduce the time required to run each fault scenario test. This approach reduces the time it takes to develop a test, reduces the number of man hours required to run the test, and decouples the initial spacecraft state from the mechanisms used to inject faults. Decoupling the initial state from the fault injection allows for easy expansion in the number of initial state/fault combinations that can be tested. This significantly improves the test coverage of the scenario test suite. Using this approach, we will be able to run more tests and increase our working knowledge of the performance of the fault protection subsystem. This paper describes the evolution, benefits and cautions of the "lights out" scenario test process.
The one-meter Testbed Telescope (TBT) has been developed at Ball Aerospace to facilitate the design and implementation of the wavefront sensing and control (WFS&C) capabilities of the James Webb Space Telescope (JWST). The TBT is used to develop and verify the WFS&C algorithms, check the communication interfaces, validate the WFS&C optical components and actuators, and provide risk reduction opportunities for test approaches for later full-scale cryogenic vacuum testing of the observatory. In addition, the TBT provides a vital opportunity to demonstrate the entire WFS&C commissioning process. This paper describes recent WFS&C commissioning experiments that have been performed on the TBT.