Determination of coating emittance at cryogenic temperatures for the James Webb Space Telescope: experimental methods and results

2005 ◽  
Author(s):  
Warren Tolson ◽  
Chuen Or ◽  
Stuart Glazer ◽  
Mark Kobel ◽  
Edward Packard
Keyword(s):  
Experimental Methods ◽  
Cryogenic Temperatures ◽  
Space Telescope ◽  
James Webb Space Telescope

Determination of emissivities of key thermo-optical surfaces on the James Webb Space Telescope

2014 ◽  
Author(s):  
Jonathan W. Arenberg ◽  
Joshua Adamson ◽  
George Harpole ◽  
Matthew Macias ◽  
Malcolm B. Niedner ◽  
...  
Keyword(s):  
Space Telescope ◽  
Optical Surfaces ◽  
James Webb Space Telescope

Analysis and Life Testing for Design of Cryogenic Bearing Assemblies on the James Webb Space Telescope Optical Telescope Element

2013 ◽  
Author(s):  
John W. Evans ◽  
Allison Barto ◽  
Benjamin Gallagher ◽  
Paul Finley ◽  
Mat Samuel ◽  
...  
Keyword(s):  
Cost Effective ◽  
Risk Tolerance ◽  
System Level ◽  
Cryogenic Temperatures ◽  
Life Testing ◽  
Optical Telescope ◽  
Space Telescope ◽  
Mission Success ◽  
James Webb Space Telescope ◽  
Effective Manner

The James Webb Space Telescope is NASA’s next generation space based telescope. The Optical Telescope Element (OTE) is an infrared system designed to operate at cryogenic temperatures. Its primary mirror consists of 18 segments; each segment is controlled by a series of actuators mounted on the back of each mirror segment. Mission success depends vitally on the actuators, specifically the critical bearing assembly of each actuator’s gear motor. This paper details the methodology employed by NASA and Ball Aerospace to evaluate the lifetime of the bearings and to design life tests which quantitatively offset risk at the system level, in a cost effective manner. The life prediction methodology utilized the Lundberg-Palmgren rule to estimate life, employing a cryogenic service factor developed from consideration of fracture toughness changes expected at cryogenic temperatures. This approach showed the capacity of the bearing system to have significant margin and reliability necessary to endure the requirements of OTE operations, over the life of JWST, under the estimated loads. Baseline test designs were subsequently developed with targets designed to show adequate risk reduction during life testing. Tests were subsequently executed at cryogenic temperatures and targets were shown to be met for the required system level risk tolerance.

scholarly journals A Spitzer Warm Mission Ultra-Wide Survey As A Target Finder For The James Webb Space Telescope

2007 ◽  
Author(s):  
Jonathan P. Gardner ◽  
Xiaohui Fan ◽  
Gillian Wilson ◽  
Massimo Stiavelli ◽  
Lisa J. Storrie-Lombardi ◽  
...  
Keyword(s):  
Space Telescope ◽  
James Webb Space Telescope

scholarly journals The diamagnetic susceptibilities of salts forming ions with inert gas configurations II-The alkaline halides

1935 ◽  
Vol 152 (876) ◽  
pp. 342-353 ◽  
Author(s):  
G. W. Brindley ◽  
F. E. Hoare ◽  
Richard Whiddington
Keyword(s):  
Crystalline State ◽  
Experimental Methods ◽  
Inert Gas ◽  
Complete Set ◽  
Sodium And Potassium ◽  
Potassium Halides

The data so far published on the diamagnetic susceptibilities of the alkaline halides, measured for the salts in the crystalline state, are very discordant and incomplete, as reference to Table I will show. The aim in carrying out these experiments has been twofold: firstly, to obtain a complete set of values for these salts and secondly to examine more closely than has hitherto been possible how rigorously the susceptibilities of simple crystalline salts are additive. It has already been established that the susceptibilities are approximately additive, but it has not been possible to test this with exactitude because of ( a ) the large discrepancies between the results obtained by previous observers, and ( b ) the lack of data for many crystals. The discrepancies may have arisen to some extent from the different experimental methods, some of which are more accurate than others and some of which may introduce errors peculiar to themselves. We have therefore made a complete re-determination of the susceptibilities of all the alkaline halides, using the same apparatus and method under the same conditions. Since any systematic experi-mental errors will affect all our results to approximately the same extent, we shall be in a stronger position for testing the additivity of the susceptibilities than if we rely partly on our own and partly on other observers’ results. Previous investigators have measured the susceptibilities of some compounds in the crystalline state and others in solution; the latter are of no help in connexion with our problem, for an examination of the available data suggests that solutions have susceptibilities higher by several per cent, than the corresponding crystals. We cannot, therefore, arrive at any certain conclusion by using results obtained partly for crystals and partly for solutions. 2—Method The method previously described has been used to obtain a complete set of values for the susceptibilities of the alkaline halides. Although slight modifications have been made from time to time, the apparatus has remained, in essentials, the same as when used for the measurement of the susceptibilities of the sodium and potassium halides.

scholarly journals The mid-infrared instrument for the James Webb Space Telescope: performance and operation of the Low-Resolution Spectrometer

2016 ◽  
Author(s):  
Sarah Kendrew ◽  
Silvia Scheithauer ◽  
Patrice Bouchet ◽  
Jerome Amiaux ◽  
Ruymán Azzollini ◽  
...  
Keyword(s):  
Low Resolution ◽  
Mid Infrared ◽  
Space Telescope ◽  
James Webb Space Telescope ◽  
Resolution Spectrometer

Observatory alignment of the James Webb Space Telescope

2012 ◽  
Author(s):  
J. Scott Knight ◽  
D. Scott Acton ◽  
Paul Lightsey ◽  
Adam Contos ◽  
Allison Barto
Keyword(s):  
Space Telescope ◽  
James Webb Space Telescope

Experimental Determination of KI for Short Internal Cracks

2001 ◽  
Vol 68 (6) ◽  
pp. 937-943 ◽  
Author(s):  
K. Bearden ◽  
J. W. Dally ◽  
R. J. Sanford
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Edge Crack ◽  
Series Solution ◽  
Experimental Studies ◽  
Experimental Methods ◽  
Internal Crack ◽  
Intensity Factors ◽  
Mode Stress

Since the pioneering discussion by Irwin, a significant effort has been devoted to determining stress intensity factors (K) using experimental methods. Techniques have been developed to determine stress intensity factors from photoelastic, strain gage, caustics, and moire´ data. All of these methods apply to a relatively long single-ended-edge crack. To date, the determination of K for internal cracks that are double-ended by experimental methods has not been addressed. This paper describes a photoelastic study of tension panels with both central and eccentric internal cracks. The data recorded in the experiments was analyzed using a new series solution for the opening-mode stress intensity factor for an internal crack. The data was also analyzed using the edge-crack series solution, which is currently employed in experimental studies. Results indicated that the experimental methods usually provided results accurate to within three to five percent if the series solution for the internal crack was employed in an overdeterministic numerical analysis of the data. Comparison of experimental results using the new series for the internal crack and the series for an edge crack showed the superiority of the new series.

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