OTE Pathfinder

Last updated

OTE Pathfinder in a test chamber James Webb Space Telescope in NASA's giant thermal vacuum chamber (17006918727).jpg
OTE Pathfinder in a test chamber

The OTE Pathfinder (for Optical Telescope Element Pathfinder), or James Webb Space Telescope Pathfinder, is a technology demonstrator and test article for the James Webb Space Telescope. [1] It is a non-flight replica of the actual backplane, but only includes the center section, not the two "wings" on the side that extend and have additional segments on the actual JWST. [2] It has been used for various tests and has some different configurations, but some of the major tests have been practicing installing mirror segments with non-flight hardware as well as thermal tests. [3] [4] The Pathfinder has also been tested in conjunction with flight hardware including the Aft Optics System. [5] One of the goals and uses of the pathfinder is risk reduction for JWST program. [6] The pathfinder allows practicing integration and testing procedures, and for risk mitigation [7] [8] With the Pathfinder it was possible to test phasing two mirrors together and also to do tests with the Aft Optical System. [9] The OTE Pathfinder was part of the plan for integration and testing of JWST, and in particular supported the Optical Telescope Element (primary mirror, backplane, etc.). [10]

Contents

The OTE pathfinder uses two additional mirror segments and an additional secondary mirror, and puts together various structures to allow testing of various aspects of the section, including Ground Support Equipment. [1] This supports the GSE's use on the JWST itself later on, and allows testing of mirror integration. [1] OTE pathfinder has 12 rather than 18 cells compared to the full telescope, but it does include a test of the backplane structure. [11] The pathfinder allowed practicing installing mirror segments with a non-flight mirror and non-flight backplane. [2] Mirror installation is a task that necessitated practice due to the high-precision required. [4]

The Pathfinder backplane was completed in 2011. [12] Three tests planned for the OTE Pathfinder were Optical Ground Support Equipment 1 (OGSE1), Optical Ground Support Equipment 2 (OGSE2), and Thermal Pathfinder. [13]

The Pathfinder was used with the Beam Image Analyzer (BIA) and another important related device is the AOS Source Plate Assembly (ASPA). [13] ASPA provides infrared sources for doing optical testing. [13]

California

The flight-replica backplane was assembled in Redondo Beach, California, at the NASA contractor Northrop Grumman facility there. [14] The flight backplane has two wings and a center section, whereas the pathfinder just as center section. [15] The backplane was transported across country (see Continental United States) in a C-5 Galaxy transport aircraft to Joint Base Andrews, and to GSC by road. [15] The section is contained with the Space Telescope Transporter for Air Road and Sea (STTARS), which was designed for the project. [16] This facilitates hauling items around the country for different tests or assembly for the JWST project. [16]

The backplane is constructed out of graphite composite, titanium, and invar. [17] Invar is an iron-nickel alloy with a low coefficient of thermal expansion (CTE or α), which means it does not significantly change size during temperature changes. [18] One of the important features of the backplane is that it is thermally stable at low temperatures, because it is holding the main mirror, it must change size less than one-ten-thousandth of a human hair (32 nm) at −240 °C (−400 °F). [17] Another test of the backplane design was the Backplane Structure Test Article, which was a one sixth portion of the full backplane. [17]

Maryland (Goddard Spaceflight Center)

The Pathfinder is unloaded from a C-5 Galaxy in 2014. The Pathfinder Backplane is contained within the white container called STTARS (this stands for Space Telescope Transporter for Air Road and Sea) James Webb Space Telescope "Pathfinder" Backplane's Path to NASA (14711591550).jpg
The Pathfinder is unloaded from a C-5 Galaxy in 2014. The Pathfinder Backplane is contained within the white container called STTARS (this stands for Space Telescope Transporter for Air Road and Sea)
Pathfinder assembled in a clean room, 2014 Smssdeploy2smlnasa.jpg
Pathfinder assembled in a clean room, 2014

In 2014 the pathfinder was transported from California to Maryland. [4] In Maryland it was used for practicing mirror installation at Goddard Space Flight Center. [19] [4] It arrived at GSC in Maryland in July 2014. [20] Mirror segments were installed on the Pathfinder, which allowed the procedure to be practiced. [21]

At Goddard Spaceflight Center the two spare main mirror segments and a spare secondary mirror were installed on the pathfinder. [21] The full James Webb Space Telescope main mirror has 18 segments (primary). [22] It was considered to use silver, however gold is more durable than silver as a coating even though it is used for reflecting down to 400 nm wavelength light; JWST is primarily for 800 nm   to 29000 nm. [22]

The Pathfinder weighed about 1,400 kilograms (3,000 lb) after the mirrors were installed. [23]

Texas (Johnson Space Center)

After the work done in Maryland at Goddard, the pathfinder was taken to Johnson Space Center in Texas, for cold environment testing. [4] The Pathfinder was delivered to JSC by early February 2015. [5] In preparation for its arrival, in 2014 Optical Ground Support Equipment was installed at the cryogenic test chamber at Johnson Space Center. [6] The ground support equipment was tested during the OGSE-1 in Chamber A at JSC, after which the Aft Optical Subsystem and Beam analyzer were installed and tested in OGSE-2. [24] The first test was completed by June 2015, and the second test was completed by November 2015. [25] The third major test, which involves even more modifications to pathfinder is called Thermal Pathfinder. [25] During the optical tests the mirrors had to be "phased" or aligned to a distance less than the wavelength of light, thousands of times smaller than the thickness of a human hair at a temperature hundreds of degree below zero. [26]

Practice makes perfect. Since we will be testing the world’s largest ever cryogenic telescope for the first time in the world’s largest cryogenic test chamber, we need to be experienced in using our test equipment so we can focus on the performance of the telescope

— Webb telescope Observatory Project Scientist [25]

By the end of October 2015 the second round of testing with JWST was completed. [27] The flight Aft Optics System was tested with the Pathfinder, and it was delivered for testing in May 2015. [5] The Aft Optics System is part of the Optical Telescope Element in the flight telescope.

In 2016 the pathfinder was used for the Pathfinder Thermal Test at Johnson Space Center in Texas. [3] At this time it had two spare flight-rated beryllium mirrors (one gold-coated) and ten non-flight gold-coated aluminum test segments functioning as thermal simulators. [3] In 2016 the pathfinder underwent thermal and vacuum tests that the actual JWST was planned to also go through in 2017. [28] The test chamber was originally built to test Apollo program hardware, but was refurbished for testing in the JWST program. [28] The thermal test will take similar hardware on cool down time line, which allows heat flow to be studied. [29] The flight JWST primary mirror is designed to be cooled down to 55 K (−218 °C; −361 °F) for operation, and the thermal tests on the pathfinder support this goal. [29] The pathfinder had to be modified for the thermal tests, including the thermal simulators to stand in for the mirrors, but also insulation. [29] There is also an Aft Optical Subsystem Geometry Simulator and an ISIM Electronics Compartment Simulator. [29] The thermal test also demonstrates the Space Vehicle Thermal Simulator (SVTS) and the Deep Space Edge Radiation Sinks (DSERS). [29]

Components

Two mirror segments of the testbed, one coated with gold one not. Silver and Gold (15224577939).jpg
Two mirror segments of the testbed, one coated with gold one not.

As a test article the exact configuration has varied somewhat as it undergoes various tests.

Components have included: [19]

See also

Related Research Articles

<span class="mw-page-title-main">First light (astronomy)</span> Term in astronomy for the first time a telescope is used to look at the Universe

In astronomy, first light is the first use of a telescope to take an astronomical image after it has been constructed. This is often not the first viewing using the telescope; optical tests will probably have been performed to adjust the components.

<span class="mw-page-title-main">James Webb Space Telescope</span> NASA/ESA/CSA space telescope launched in 2021

The James Webb Space Telescope (JWST) is a space telescope designed to conduct infrared astronomy. Its high-resolution and high-sensitivity instruments allow it to view objects too old, distant, or faint for the Hubble Space Telescope. This enables investigations across many fields of astronomy and cosmology, such as observation of the first stars and the formation of the first galaxies, and detailed atmospheric characterization of potentially habitable exoplanets.

<span class="mw-page-title-main">Grism</span> Optical element that reflects and diffracts light

A grism is a combination of a prism and grating arranged so that light at a chosen central wavelength passes straight through. The advantage of this arrangement is that one and the same camera can be used both for imaging and spectroscopy without having to be moved. Grisms are inserted into a camera beam that is already collimated. They then create a dispersed spectrum centered on the object's location in the camera's field of view.

OTE is the national telecommunications provider of Greece.

<span class="mw-page-title-main">Segmented mirror</span> Array of smaller mirrors designed to act as one large curved mirror

A segmented mirror is an array of smaller mirrors designed to act as segments of a single large curved mirror. The segments can be either spherical or asymmetric. They are used as objectives for large reflecting telescopes. To function, all the mirror segments have to be polished to a precise shape and actively aligned by a computer-controlled active optics system using actuators built into the mirror support cell.

<span class="mw-page-title-main">Fine guidance sensor</span> Space telescope pointing device

A fine guidance sensor (FGS) is an instrument on board a space telescope that provides high-precision pointing information as input to the telescope's attitude control systems. Interferometric FGSs have been deployed on the Hubble Space Telescope; a different technical approach is used for the James Webb Space Telescope's FGSs. In some specialized cases, such as astrometry, FGSs can also be used as scientific instruments.

<span class="mw-page-title-main">Test article (aerospace)</span> Vehicle or equipment used to test portions of a spaceflight regime

A test article or pathfinder is a version of a spacecraft or related vehicle or equipment, built as a platform to perform testing on particular portions of a spaceflight regime. Test articles are built to the specifications necessary to replicate particular conditions and behaviors that are to be validated. Test articles may be built for flight testing or for non-flight testing.

LIDAX is a space technology company, founded at the beginning of the year 2000. It designs and manufactures advanced mechanical equipments that form part of complex space flight systems and instruments for Earth observation, planetary exploration (Exomars), astrophysics instrumentation and telecom. The activities of the company encompass all aspects, from conceptual design, through integration and testing up to realization; both for satellite and on-ground instrumentation.

<span class="mw-page-title-main">Matt Mountain</span> President of the Association of Universities for Research in Astronomy

Charles Mattias ("Matt") Mountain is currently the President of the Association of Universities for Research in Astronomy (AURA) which designs, builds, and operates telescopes and observatories for the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA). AURA's NASA center is the Space Telescope Science Institute (STScI), responsible for the science mission for the Hubble Space Telescope, the science and operations for the James Webb Space Telescope, and the MAST data archive. AURA's NSF centers are Gemini Observatory, the National Optical Astronomy Observatory (NOAO), and the National Solar Observatory (NSO). Dr. Mountain and AURA are also responsible for the NSF construction projects: the Daniel K. Inouye Solar Telescope (DKIST) on Haleakalā, Hawaii and the Large Synoptic Survey Telescope (LSST) on Cerro Pachón in Chile.

<span class="mw-page-title-main">NIRSpec</span> Spectrograph on the James Webb Space Telescope

The NIRSpec is one of the four scientific instruments flown on the James Webb Space Telescope (JWST). The JWST is the follow-on mission to the Hubble Space Telescope (HST) and is developed to receive more information about the origins of the universe by observing infrared light from the first stars and galaxies. In comparison to HST, its instruments will allow looking further back in time and will study the so-called Dark Ages during which the universe was opaque, about 150 to 800 million years after the Big Bang.

<span class="mw-page-title-main">Large Ultraviolet Optical Infrared Surveyor</span> Proposed NASA space telescope

The Large Ultraviolet Optical Infrared Surveyor, commonly known as LUVOIR, is a multi-wavelength space telescope concept being developed by NASA under the leadership of a Science and Technology Definition Team. It is one of four large astrophysics space mission concepts studied in preparation for the National Academy of Sciences 2020 Astronomy and Astrophysics Decadal Survey.

<span class="mw-page-title-main">Timeline of the James Webb Space Telescope</span> Timeline of notable events of the development of the James Webb Space Telescope

The James Webb Space Telescope (JWST) is an international 21st-century space observatory that was launched on 25 December 2021. It is intended to be the premier observatory of the 2020s, combining the largest mirror yet on a near-infrared space telescope with a suite of technologically advanced instruments from around the world.

<span class="mw-page-title-main">Fine Guidance Sensor and Near Infrared Imager and Slitless Spectrograph</span> Canadian aligner and spectrometer on JWST

Fine Guidance Sensor and Near Infrared Imager and Slitless Spectrograph (FGS-NIRISS) is an instrument on the James Webb Space Telescope (JWST) that combines a Fine Guidance Sensor and a science instrument, a near-infrared imager and a spectrograph. The FGS/NIRISS was designed by the Canadian Space Agency (CSA) and built by Honeywell as part of an international project to build a large infrared space telescope with the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA). FGS-NIRISS observes light from the wavelengths of 0.8 to 5.0 microns. The instrument has four different observing modes.

<span class="mw-page-title-main">Integrated Science Instrument Module</span> Part of the James Webb Space Telescope

Integrated Science Instrument Module (ISIM) is a component of the James Webb Space Telescope, a large international infrared space telescope launched on 25 December 2021. ISIM is the heart of the JWST, and holds the main science payload which includes four science instruments and the fine guidance sensor.

<span class="mw-page-title-main">Optical Telescope Element</span> Subsection of the James Webb Space Telescope

Optical Telescope Element (OTE) is a sub-section of the James Webb Space Telescope, a large infrared space telescope launched on 25 December 2021, consisting of its main mirror, secondary mirrors, the framework and controls to support the mirrors, and various thermal and other systems.

<span class="mw-page-title-main">NIRCam</span> Imaging instrument aboard the James Webb Space Telescope

NIRCam is an instrument aboard the James Webb Space Telescope. It has two major tasks, as an imager from 0.6 to 5 micron wavelength, and as a wavefront sensor to keep the 18-section mirrors functioning as one. In other words, it is a camera and is also used to provide information to align the 18 segments of the primary mirror. It is an infrared camera with ten mercury-cadmium-telluride (HgCdTe) detector arrays, and each array has an array of 2048×2048 pixels. The camera has a field of view of 2.2×2.2 arc minutes with an angular resolution of 0.07 arcsec at 2 microns. NIRCam is also equipped with coronagraphs, which helps to collect data on exoplanets near stars. It helps with imaging anything next to a much brighter object, because the coronagraph blocks that light.

<span class="mw-page-title-main">James Webb Space Telescope sunshield</span> Main cooling system for the infrared observatory

The James Webb Space Telescope (JWST) sunshield is a passive thermal control system deployed post-launch to shield the telescope and instrumentation from the light and heat of the Sun, Earth, and Moon. By keeping the telescope and instruments in permanent shadow, it allows them to cool to their design temperature of 40 kelvins. Its intricate deployment was successfully completed on January 4, 2022, ten days after launch, when it was more than 0.8 million kilometers (500,000 mi) away from Earth.

<span class="mw-page-title-main">Spacecraft bus (James Webb Space Telescope)</span> Part of the James Webb Space Telescope

The spacecraft bus is a carbon fibre box that houses systems of the telescope and so is the primary support element of the James Webb Space Telescope, launched on 25 December 2021. It hosts a multitude of computing, communication, propulsion, and structural components. The other three elements of the JWST are the Optical Telescope Element (OTE), the Integrated Science Instrument Module (ISIM) and the sunshield. Region 3 of ISIM is also inside the spacecraft bus. Region 3 includes the ISIM Command and Data Handling subsystem and the Mid-Infrared Instrument (MIRI) cryocooler.

<span class="mw-page-title-main">Infrared Array Camera</span>

The Infrared Array Camera (IRAC) was an infrared camera system on the Spitzer Space Telescope which operated in the mid-infrared spectrum. It was composed of four detectors that operated simultaneously at different wavelengths; all four were in use until 2009 May 15 when the Spitzer cryostat ran out of liquid helium. After then, the spacecraft operated in a warm extended mission, in which two of the four detectors remained functional, until the Spitzer mission was terminated on 2020 January 30.

<span class="mw-page-title-main">Launch and commissioning of the James Webb Space Telescope</span>

The James Webb Space Telescope (JWST) is a space telescope designed primarily to conduct infrared astronomy. Its complex launch and commissioning process lasted from late 2021 until mid-2022.

References

  1. 1 2 3 Feinberg, Lee D.; Keski-Kuha, Ritva; Atkinson, Charlie; Booth, Andrew; Whitman, Tony (2014). "James Webb Space Telescope (JWST) Optical Telescope Element (OTE) Pathfinder status and plans". In Oschmann, Jacobus M; Clampin, Mark; Fazio, Giovanni G; MacEwen, Howard A (eds.). Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave. Vol. 9143. pp. 91430E. doi:10.1117/12.2054782. S2CID   121581750 . Retrieved 5 December 2016.
  2. 1 2 Jenner, Lynn (12 August 2014). "James Webb Space Telescope "Pathfinder" Backplane's Path to NASA". NASA. Retrieved 6 February 2017.
  3. 1 2 3 4 Loff, Sarah (29 September 2016). "Testing the James Webb Space Telescope Pathfinder". NASA. Retrieved 27 January 2017.
  4. 1 2 3 4 5 Jenner, Lynn (12 August 2014). "James Webb Space Telescope "Pathfinder" Backplane's Path to NASA". NASA. Retrieved 27 January 2017.
  5. 1 2 3 "Recent Accomplishments JWST/NASA". NASA. Retrieved 6 February 2017.
  6. 1 2 Matthews, Gary W.; Scorse, Thomas R.; Spina, John A.; Noël, Darin M.; Havey, Keith A.; Huguet, Jesse A.; Whitman, Tony L.; Wells, Conrad; Walker, Chanda B. (1 August 2015). Fähnle, Oliver W; Williamson, Ray; Kim, Dae Wook (eds.). JWST pathfinder telescope risk reduction cryo test program. Optical Manufacturing and Testing XI. Vol. 9575. p. 957505. Bibcode:2015SPIE.9575E..05M. doi:10.1117/12.2188793. hdl: 2060/20150018095 . ISSN   0277-786X. S2CID   117482013.
  7. ↑ Optical Telescope Element Pathfinder
  8. ↑ Feinberg, Lee D.; Keski-Kuha, Ritva; Atkinson, Charlie; Texter, Scott C. (11 August 2010). "Use of a pathfinder optical telescope element for James Webb Space Telescope risk mitigation". In Oschmann, Jr, Jacobus M; Clampin, Mark C; MacEwen, Howard A (eds.). Space Telescopes and Instrumentation 2010: Optical, Infrared, and Millimeter Wave. Vol. 7731. SPIE. pp. 1347–1355. doi:10.1117/12.855800. hdl:2060/20100024388. S2CID   120930911 – via www.spiedigitallibrary.org.
  9. ↑ Status of the James Webb Space Telescope (JWST) Observatory
  10. ↑ Phil Sabelhaus: JWST Project Status for the CAA, May 20, 2006
  11. ↑ SatMagazine, February 2012: The Untold Story Of NASA’s James Webb Space Telescope
  12. ↑ "NASA - NASA's James Webb Space Telescope: A Year of Achievement and Success". NASA. Retrieved 6 February 2017.
  13. 1 2 3 James Webb Space Telescope (JWST) Optical Telescope Element (OTE) Pathfinder Status and Plans
  14. ↑ Jenner, Lynn (12 August 2014). "James Webb Space Telescope "Pathfinder" Backplane's Path to NASA". NASA.
  15. 1 2 Jenner, Lynn (12 August 2014). "James Webb Space Telescope "Pathfinder" Backplane's Path to NASA". NASA. Retrieved 8 February 2017.
  16. 1 2 McKinnon, Mika. "This Custom Shipping Container For Telescope Parts Is Fantastic". Gizmodo. Retrieved 8 February 2017.
  17. 1 2 3 Administrator, NASA (7 June 2013). "James Webb Space Telescope's Actual 'Spine' Now Being Built". NASA.
  18. ↑ Davis, Joseph R. (2001). Alloying: Understanding the Basics . ASM International. pp.  587–589. ISBN   0-87170-744-6.
  19. 1 2 "The James Webb Space Telescope". NASA. Retrieved 27 January 2017.
  20. ↑ Loff, Sarah (27 February 2015). "James Webb Space Telescope "Pathfinder" Backplane in the Cleanroom". NASA. Retrieved 27 January 2017.
  21. 1 2 Loff, Sarah (27 February 2015). "James Webb Space Telescope "Pathfinder" Backplane in the Cleanroom". NASA.
  22. 1 2 Keski-Kuha, Ritva A.; Bowers, Charles W.; Quijada, Manuel A.; Heaney, James B.; Gallagher, Benjamin; McKay, Andrew; Stevenson, Ian (3 July 2012). Clampin, Mark C; Fazio, Giovanni G; MacEwen, Howard A; Oschmann, Jacobus M (eds.). "James Webb Space Telescope Optical Telescope Element Mirror Coatings" (PDF). Space Telescopes and Instrumentation 2012: Optical. Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave. 8442: 84422J. Bibcode:2012SPIE.8442E..2JK. doi:10.1117/12.925470. hdl:2060/20120013496. S2CID   121231936 – via ntrs.nasa.gov.
  23. ↑ "How NASA Is Readying the Successor to the Hubble Space Telescope". ABC News.
  24. ↑ Feinberg, Lee D.; Keski-Kuha, Ritva; Atkinson, Charlie; Booth, Andrew; Whitman, Tony (2 August 2014). "James Webb Space Telescope (JWST) Optical Telescope Element (OTE) Pathfinder status and plans". In Oschmann, Jacobus M; Clampin, Mark; Fazio, Giovanni G; MacEwen, Howard A (eds.). Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave. Vol. 9143. pp. 91430E. doi:10.1117/12.2054782. S2CID   121581750.
  25. 1 2 3 Jenner, Lynn (30 November 2015). "NASA's Webb Successfully Completes Second Super-Cold Optical Test". NASA.
  26. ↑ Jenner, Lynn (15 October 2015). "Webb "Pathfinder Telescope" Has Super-Cold Optics Test Success". NASA. Retrieved 8 February 2017.
  27. ↑ "Recent Accomplishments JWST/NASA". NASA. Retrieved 27 January 2017.
  28. 1 2 "Preparing JWST for launch". Space Daily. Retrieved 27 January 2017.
  29. 1 2 3 4 5 James Webb Space Telescope Thermal Pathfinder Test Development, International Conference on Environmental Systems
  30. ↑ "NASA's James Webb Space Telescope: A Year of Achievement and Success". NASA. Retrieved 27 January 2017.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.