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Howard, Joseph

Publications and source records attributed to Howard, Joseph.

18 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

Optical Design of the Origins Space Telescope

The optical design is presented for the Origins Space Telescope, one of four large missions under study in preparation for the 2020 Decadal Survey in Astronomy and Astrophysics is presented. Sensitive to the mid- and far-infrared spectrum (between 2.8 and 588 µm) and set to launch in approximately 2035, Origins sets out to answer a number of important scientific questions by addressing NASA's three key science goals in astrophysics: How does the universe work?, How did we get here, and Are we alone? To do so, Origins seeks to answer three main questions: 1) How do galaxies form stars, build up metals, and grow their central supermassive black holes from reionization to today? 2) How do the conditions for habitability develop during the process of planet formation? 3) Do planets orbiting M-dwarf stars support life?The Origins telescope has a 5.9 m diameter primary mirror and operates at f/14. The large on-axis primary consists of 18 'keystone' segments of two different prescriptions arranged in two annuli (six inner and twelve outer segments) that together form a circular aperture in the goal of achieving a symmetric point spread function. To simplify the design, the telescope will be launched with both the primary mirror segments and the secondary mirror already deployed. To accommodate the 46 x 15 arcminute full field of view of the telescope at the design wavelength of = 30 µm, a three-mirror anastigmat configuration is used. The design is diffraction-limited across its instruments' fields of view. A brief discussion of each of the three baselined instruments within the Instrument Accommodation Module (IAM) is presented: 1) Origins Survey Spectrometer (OSS), 2) Mid-infrared Spectrometer, Camera (MISC) transit spectrometer channel, and 3) Far-Infrared Polarimeter/Imager (FIP). In addition, the upscope options for the observatory are laid out as well, including a fourth instrument: the Heterodyne Receiver for Origins (HERO).

Howard, Joseph↗
NASA NTRS2016

Dual-Telescope Multi-Channel Thermal-Infrared Radiometer for Outer Planet Fly-By Missions

The design of a versatile dual-telescope thermal-infrared radiometer spanning the spectral wavelength range 8-200 microns, in five spectral pass bands, for outer planet fly-by missions is described. The dual- telescope design switches between a narrow-field-of-view and a wide-field-of-view to provide optimal spatial resolution images within a range of spacecraft encounters to the target. The switchable dual-field- of-view system uses an optical configuration based on the axial rotation of a source-select mirror along the optical axis. The optical design, spectral performance, radiometric accuracy, and retrieval estimates of the instrument are discussed. This is followed by an assessment of the surface coverage performance at various spatial resolutions by using the planned NASA Europa Mission 13-F7 fly-by trajectories as a case study.

Aslam, Shahid↗
NASA NTRS2016

Structural, Thermal, and Optical Performance (STOP) Modeling and Results for the James Webb Space Telescope Integrated Science Instrument Module

The James Webb Space Telescope includes the Integrated Science Instrument Module (ISIM) element that contains four science instruments (SI) including a Guider. We performed extensive structural, thermal, and optical performance(STOP) modeling in support of all phases of ISIM development. In this paper, we focus on modeling and results associated with test and verification. ISIMs test program is bound by ground environments, mostly notably the 1g and test chamber thermal environments. This paper describes STOP modeling used to predict ISIM system performance in 0g and at various on-orbit temperature environments. The predictions are used to project results obtained during testing to on-orbit performance.

structural↗
NASA NTRS2015

Freeform Optical Design of Two Mirror Telescopes

Two Mirror telescopes composed of freeform optical surfaces are investigated and surveyed to explore the usable design space. F-number and field of view are evaluated and plotted. A case study is presented to show the benefits of volume reduction using freeform surfaces.

Optical Design↗
NASA NTRS2014

Optical Design of WFIRST-AFTA Wide-Field Instrument

The WFIRSTAFTA Wide-Field Infrared Survey Telescope TMA optical design provides 0.28-sq FOV at 0.11 pixel scale, operating between 0.6 2.4m, including a spectrograph mode (1.3-1.95m.) An IFU provides a discrete 3x3.15 field at 0.15 sampling.

Optical Equipment↗
NASA NTRS2012

Rapid Process to Generate Beam Envelopes for Optical System Analysis

The task of evaluating obstructions in the optical throughput of an optical system requires the use of two disciplines, and hence, two models: optical models for the details of optical propagation, and mechanical models for determining the actual structure that exists in the optical system. Previous analysis methods for creating beam envelopes (or cones of light) for use in this obstruction analysis were found to be cumbersome to calculate and take significant time and resources to complete. A new process was developed that takes less time to complete beam envelope analysis, is more accurate and less dependent upon manual node tracking to create the beam envelopes, and eases the burden on the mechanical CAD (computer-aided design) designers to form the beam solids. This algorithm allows rapid generation of beam envelopes for optical system obstruction analysis. Ray trace information is taken from optical design software and used to generate CAD objects that represent the boundary of the beam envelopes for detailed analysis in mechanical CAD software. Matlab is used to call ray trace data from the optical model for all fields and entrance pupil points of interest. These are chosen to be the edge of each space, so that these rays produce the bounding volume for the beam. The x and y global coordinate data is collected on the surface planes of interest, typically an image of the field and entrance pupil internal of the optical system. This x and y coordinate data is then evaluated using a convex hull algorithm, which removes any internal points, which are unnecessary to produce the bounding volume of interest. At this point, tolerances can be applied to expand the size of either the field or aperture, depending on the allocations. Once this minimum set of coordinates on the pupil and field is obtained, a new set of rays is generated between the field plane and aperture plane (or vice-versa). These rays are then evaluated at planes between the aperture and field, at a desired number of steps perceived necessary to build up the bounding volume or cone shape. At each plane, the ray coordinates are again evaluated using the convex hull algorithm to reduce the data to a minimal set. When all of the coordinates of interest are obtained for every plane of the propagation, the data is formatted into an xyz file suitable for FRED optical analysis software to import and create a STEP file of the data. This results in a spiral-like structure that is easily imported by mechanical CAD users who can then use an automated algorithm to wrap a skin around it and create a solid that represents the beam.

Howard, Joseph↗
NASA NTRS2010

Optical Design Process and Comparison for ATLAST Concepts

The ATLAST (Advanced Technology for Large Aperture Space Telescopes) effort has presented several design incarnations. Here we will discus the design process in detail and compare the design and performance of the 9.2m segmented, the 8m monolithic on-axis and 8m x 6m off-axis concepts

Pasquale, Bert A.↗
NASA NTRS2010

Comparative Concepts for ATLAST Optical Designs

The ATLAST (Advanced Technology for Large Aperture Space Telescopes) effort has presented several design incarnations. Here we will compare the design and performance of the 9.2m segmented, the 8m monolithic on-axis and 8m x 6m off-axis concepts.

Pasquale, Bert A.↗
NASA NTRS2008

New Worlds Observer Telescope and Instrument Optical Design Concepts

Optical design concepts for the telescope and instrumentation for NASA's New Worlds Observer program are presented. First order parameters are derived from the science requirements, and estimated performance metrics are shown using optical models. A four meter multiple channel telescope is discussed, as well as a suite of science instrument concepts. Wide field instrumentation (imager and spectrograph) would be accommodated by a three-mirror anastigmat telescope design. Planet finding and characterization would use a separate channel which is picked off after the first two mirrors (primary and secondary). Guiding concepts are also discussed.

Howard, Joseph↗
NASA NTRS2007

Optical Modeling Activities for NASA's James Webb Space Telescope (JWST): Overview and Introduction of Matlab Based Toolkits used to Interface with Optical Design Software - 4

This is part four of a series on the ongoing optical modeling activities for James Webb Space Telescope (JWST). The first two discussed modeling JWST on-orbit performance using wavefront sensitivities to predict line of sight motion induced blur, and stability during thermal transients. The third investigates the aberrations resulting from alignment and figure compensation of the controllable degrees of freedom (primary and secondary mirrors), which may be encountered during ground alignment and on-orbit commissioning of the observatory. The work here introduces some of the math software tools used to perform the work of the previous three papers of this series. NASA has recently approved these in-house tools for public release as open source, so this presentation also serves as a quick tutorial on their use. The tools are collections of functions written in Matlab, which interface with optical design software (CodeV, OSLO, and Zemax) using either COM or DDE communication protocol. The functions are discussed, and examples are given.

Howard, Joseph↗
NASA NTRS2007

Matlab based Toolkits used to Interface with Optical Design Software for NASA's James Webb Space Telescope

The viewgraph presentation provides an introduction to the James Webb Space Telescope (JWST). The first part provides a brief overview of Matlab toolkits including CodeV, OSLO, and Zemax Toolkits. The toolkit overview examines purpose, layout, how Matlab gets data from CodeV, function layout, and using cvHELP. The second part provides examples of use with JWST, including wavefront sensitivities and alignment simulations.

Howard, Joseph↗
NASA NTRS2007

Wavefront Aberrations Due to Alignment and Figure Compensation of the NASA James Webb Space Telescope

This viewgraph presentation describes wavefront aberrations due to the alignment and improper compensation of the NASA James Webb Space Telescope. The contents include: 1) James Webb Space Telescope (JWST); 2) Optical design of JWST; 3) Alignment Observables for JWST; 4) Low order Zernike Polynomials; 5) PM SM Ability to Target Low Order Aberrations; 6) Compensator definitions and Modes; 7) Field impact from compensation; 8) PM align error compensated by PM figure; 9) PM align error compensated by SM alignment; 10) SM align error compensated by PM figure; 11) SM figure error compensated by SM alignment; 12) Worst Case Pupil Maps; 13) Worst Case Pupil Maps at BEST FOCUS; 14) Field impact from compensation (+/- 1 arcmin FOV); and 15) Concluding Remarks.

Howard, Joseph↗
NASA NTRS2007

Optical Modeling Activities for NASA's James Webb Space Telescope (JWST): Wavefront Aberrations due to Alignment and Figure Compensation - 3

This is part three of a series describing the ongoing optical modeling activities for James Webb Space Telescope (JWST). The first two discussed modeling JWST on-orbit performance using wavefront sensitivities to predict line of sight motion induced blur, and stability during thermal transients. The work here investigates the aberrations resulting from alignment and figure compensation of the controllable degrees of freedom (primary and secondary mirrors), which may be encountered during ground alignment and on-orbit commissioning of the observatory. The optical design of the telescope is a three-mirror anastigmat, with an active fold mirror at the exit pupil for fine guiding. The primary mirror is over 6.5 meters in diameter, and is composed of 18 hexagonal segments that can individually positioned on hexapods, as well as compensated for radius of curvature. This effectively gives both alignment and figure control of the primary mirror. The secondary mirror can be moved in rigid body only, giving alignment control of the telescope. The tertiary mirror is fixed, however, as well as the location of the science instrumentation. Simulations are performed of various combinations of active alignment corrections of component figure errors, and of primary mirror figure corrections of alignment errors. Single field point and moderate field knowledge is assumed in the corrections. Aberrations over the field are reported for the varying cases, and examples presented.

Howard, Joseph↗
NASA NTRS2006

Best Practices for Operations of Satellite Constellations

This paper presents the best practices used by several commercial and government operators of satellite constellations. These best practices were identified through a series of seminars and discussions held at NASA Goddard Space Flight Center (GSFC). The best practices are arrived through many years of experience and improvements made in the operations procedures and the operational systems with the primary drivers as mission safety and cost effectiveness. This paper discusses the operational aspects associated with how different organizations manage complexities of constellation operations. For the purposes of this paper, satellite constellations are groups of similar spacecraft with more than one spacecraft needed to fully accomplish the constellation's mission

Howard, Joseph↗
NASA NTRS2004

Requirements Formulation and Dynamic Jitter Analysis for Fourier-Kelvin Stellar Interferometer

The Fourier-Kelvin Stellar Interferometer (FKSI) has been proposed to detect and characterize extra solar giant planets. The baseline configuration for FKSI is a two- aperture, structurally connected nulling interferometer, capable of providing null depth less than lo4 in the infrared. The objective of this paper is to summarize the process for setting the top level requirements and the jitter analysis performed on FKSI to date. The first part of the paper discusses the derivation of dynamic stability requirements, necessary for meeting the FKSI nulling demands. An integrated model including structures, optics, and control systems has been developed to support dynamic jitter analysis and requirements verification. The second part of the paper describes how the integrated model is used to investigate the effects of reaction wheel disturbances on pointing and optical path difference stabilities.

Liu, Kuo-Chia↗
NASA NTRS2004

Design and Analysis of FKSI Nulling Interferometry Testbed

The Fourier Kelvin Stellar Interferometer is a space borne mission whose purpose is to validate the existence of previously detected Extra Solar Giant Planets (EGP's) and determine the age and primary atmospheric constituents of these EGP's. It consists of 2 collecting telescopes followed by a Mach Zehnder interferometer working in a wavelength range of 3-8 microns. To support this concept, a testbed is being built at NASA Goddard Space Flight Center to demonstrate feasibility of achieving the required nulling ratio (10e-4) across the waveband. This paper describes the design and performance analysis of the testbed. Considerations such as polarization, pupil overlap, and optical path length control are discussed.

Wilson, Mark↗
NASA NTRS2000

Lessons Learned on Operating and Preparing Operations for a Technology Mission from the Perspective of the Earth Observing-1 Mission

The New Millennium Program's first Earth-observing mission (EO-1) is a technology validation mission. It is managed by the NASA Goddard Space Flight Center in Greenbelt, Maryland and is scheduled for launch in the summer of 2000. The purpose of this mission is to flight-validate revolutionary technologies that will contribute to the reduction of cost and increase of capabilities for future land imaging missions. In the EO-1 mission, there are five instrument, five spacecraft, and three supporting technologies to flight-validate during a year of operations. EO-1 operations and the accompanying ground system were intended to be simple in order to maintain low operational costs. For purposes of formulating operations, it was initially modeled as a small science mission. However, it quickly evolved into a more complex mission due to the difficulties in effectively integrating all of the validation plans of the individual technologies. As a consequence, more operational support was required to confidently complete the on-orbit validation of the new technologies. This paper will outline the issues and lessons learned applicable to future technology validation missions. Examples of some of these include the following: (1) operational complexity encountered in integrating all of the validation plans into a coherent operational plan, (2) initial desire to run single shift operations subsequently growing to 6 "around-the-clock" operations, (3) managing changes in the technologies that ultimately affected operations, (4) necessity for better team communications within the project to offset the effects of change on the Ground System Developers, Operations Engineers, Integration and Test Engineers, S/C Subsystem Engineers, and Scientists, and (5) the need for a more experienced Flight Operations Team to achieve the necessary operational flexibility. The discussion will conclude by providing several cost comparisons for developing operations from previous missions to EO-1 and discuss some details that might be done differently for future technology validation missions.

Mandl, Dan↗