221 research outputs found
Optical Budgeting for LUVOIR
Future large astronomical telescopes in space will have architectures that will have complex and demanding requirements to meet the science goals. The Large UV/Optical/IR Surveyor (LUVOIR) mission concept being assessed by the NASA/Goddard Space Flight Center is expected to be 8 to 16 meters in diameter, have a segmented primary mirror, active control, and be diffraction limited at a wavelength of 500 nanometers. The optical stability is expected to be in the picometer range for minutes to hours. Architecture studies to support the NASA Science and Technology Definition teams (STDTs) are underway to evaluate systems performance. A wave front error budget has been developed to help define the technology needs and assess performance. The budget includes both spatial and temporal domain aspects for the active, adaptive and passive elements in the optical design
Active X-ray Optics for Generation-X, the Next High Resolution X-ray Observatory
X-rays provide one of the few bands through which we can study the epoch of
reionization, when the first galaxies, black holes and stars were born. To
reach the sensitivity required to image these first discrete objects in the
universe needs a major advance in X-ray optics. Generation-X (Gen-X) is
currently the only X-ray astronomy mission concept that addresses this goal.
Gen-X aims to improve substantially on the Chandra angular resolution and to do
so with substantially larger effective area. These two goals can only be met if
a mirror technology can be developed that yields high angular resolution at
much lower mass/unit area than the Chandra optics, matching that of
Constellation-X (Con-X). We describe an approach to this goal based on active
X-ray optics that correct the mid-frequency departures from an ideal Wolter
optic on-orbit. We concentrate on the problems of sensing figure errors,
calculating the corrections required, and applying those corrections. The time
needed to make this in-flight calibration is reasonable. A laboratory version
of these optics has already been developed by others and is successfully
operating at synchrotron light sources. With only a moderate investment in
these optics the goals of Gen-X resolution can be realized.Comment: Enhanced version of SPIE presentation. 11 pages, 5 figure
Fast Steering Mirror Disturbance Effects on Overall System Optical Performance for the Large Ultraviolet/optical/infrared Surveyor (LUVOIR) Concept Using a Non-Contact Vibration Isolation and Precision Pointing System
As the optical performance requirements of space telescopes get more stringent, the need to analyze all possible error sources early in the mission design becomes critical. One large telescope with tight performance requirements is the Large Ultraviolet / Optical / Infrared Surveyor (LUVOIR) concept. The LUVOIR concept includes a 15-meter-diameter segmented-aperture telescope with a suite of serviceable instruments operating over a range of wavelengths between 100nm to 2.5um. Using an isolation architecture that involves no mechanical contact between the telescope and the host spacecraft structure allows for tighter performance metrics than current space-based telescopes being flown. Because of this separation, the spacecraft disturbances can be greatly reduced and disturbances on the telescope payload contribute more to the optical performance error. A portion of the optical performance error comes from the disturbances generated from the motion of the Fast Steering Mirror (FSM) on the payload. Characterizing the effects of this disturbance gives insight into the specifications on the FSM needed to achieve the tight optical performance requirements of the overall system. Through analysis of the LUVOIR finite element model and linear optical model given a range of input disturbances at the FSM, the optical performance of the telescope and recommendations for FSM specifications can be determined. The LUVOIR observatory control strategy consists of a multi-loop control architecture including the spacecraft Attitude Control System (ACS), Vibration Isolation and Precision Pointing System (VIPPS), and FSM. This paper focuses on the control loop containing the FSM disturbances and their effects on the telescope optical performance
The Technological culture of war
The article proceeds from the argument that war is a social institution and not a historical inevitability of human interaction,
that is, war can be “unlearned.” This process involves deconstructing/dismantling war as an institution in
society. An important step in this process is to understand the philosophical and cultural bases on which technology
is employed as “tools” of war. The article focuses on such questions as, Is technology just viewed as instruments in
the hand of its human masters in war? Does technology take on an autonomous role in war? How should we assess
the impact of context (political, economic, and cultural) of technology when employed in war? By exploring these
points, the article hopes to provide input into the discussion on the control of war technologies and ultimately the dismantling
of war as an institution in society
The Electronically Activated Recorder (EAR): A device for sampling naturalistic daily activities and conversations
Relationship Between Self-Reported Health and Stress in Mothers of Children with Autism Spectrum Disorders
Empowerment and Parent Gain as Mediators and Moderators of Distress in Mothers of Children with Autism Spectrum Disorders
Mothers of children with Autism Spectrum Disorders (ASD) experience considerable amounts of distress and experiences of crisis. The Family Adjustment and Adaptation Response model provides a theory for understanding the experience of distress and family crisis in families, and the purpose of the present study was to examine experiences of distress in mothers of individuals with ASD using this framework. We specifically investigated how parent empowerment and positive gain are related to their experiences of distress, whether as mediators or as moderators of child aggression. Participants included 156 mothers of children with ASD ranging in age from 4 – 21 years. Mothers completed an online survey of demographics, problem behaviors, family empowerment, positive gain, and distress. We conducted path analyses of multiple mediation and moderation. Results indicated that greater child problem behavior was related to less parent empowerment, which was related to greater maternal distress, supporting empowerment as a partial mediator. At the same time, greater child aggression was not related to maternal distress in mothers who report high rates of positive gain, suggesting that parent gain functions as a moderator. The implications for how and when clinicians intervene with families of children with ASD are discussed
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