Jianing life in it. They built the OSRIS-REx

Jianing ZhangProfessor PommierSIO 125 January 2018 The OSIRIS-RExVisible and Infrared Spectrometer (OVIRS): Osiris-REX – AsteroidsFig. 0. NASA,et al.

“OSIRIS-REx Technology: OVIRS.” NASA, NASA, 25 July 2016,svs.gsfc.nasa.gov/12309.

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OSIRIS-REx is the thirdmission of NASA’s New Frontiers Program conducted by NASA’s Marshall SpaceFlight Center in Huntsville. The spaceship is built in Lockheed Martin SpaceSystems in Denver and OSISRIS-REx sicence Processing and Operations Center areat the University of Arizona, NASA’s Goddard Space Flight Center in Greenbelt.The instrument, OSRIS-REx Visible and infrared Spectrometer (OVIRS) will bediscussed in this report.Purpose& Scientific QuestionsIn the mission of sendingOSRIS-REx spacecraft to an asteroid Benuu that is rich of carbon material,scientists are hoping to find the origins of life in it. They built theOSRIS-REx Visible and infrared Spectrometer (OVIRS) to look at asteroid Benuu’sspectral signature to detect minerals and organics. It breaks down light intoseparate individual wavelength packets in order for the scientists to analyzefrom the details of spectra to tell which material they are looking for.

OVIRSwill work along with another instrument, the Thermal Emission Spectrometer(OTES). With information collected by OVIRS and OTES, scientists will alsostudy the Yarkovsky effect, which is how surface heating and cooling willaffect Bennu’s orbit. Mechanismsof InstrumentsOVIRS is a spectrometerequipped with a 4-mrad field of view providing wavelength range of 0.4 – 4.3um. It has a wedged two-dimensional spectral filter (linearly variable, LVF)that could detect varies of substances.

In LVF, wavelength of the transmittedlight will wary in one dimension. The filter segments will be put on anassembly placed over the detector. It has a spectral resolution defined asresolving power, R. Resolving Power Spectral Range(?m) R>= 125 0.4 to 1.1 R>= 150 1.1 to 2.

0 R>= 200 2.0 to 4.3 R>= 350 2.9 to 3.6  With this resolution,OVIRS could provide data of many mineral and molecular components such assulfates, oxides, canbonates, silicates, water and many organic species. Itwill provide spectral data for the asteroid, spectral maps with 20m resolution.

It will provide two spectral samples for each spectral resolution element tomake a full use of it.Fig. 1. Reuter, D.C., et al. “The OSIRIS-REx Visible and InfraRedSpectrometer (OVIRS): Spectral Maps of the Asteroid Bennu.

” CornellUniversity Library, Cornell University Library, 30 Mar. 2017,arxiv.org/abs/1703.

10574.The shape of graph wasdetermined for the filter focal plane assembly with multi-order grating. Thus,it could generate a table of wavelength and resolving power. Figure 11 shows anexample of the readout of LVF segments with the output of a gratingmonochromator. The three peaks matched to order of six to four of 4 ?m grating. Two lines shows theprogress of changing grating setting to pass through a spectral element…Wecould see from data of the instrument and determine that the line shape isGaussian.

OVIRS is equipped with anoff-axis parabolic mirror(OAP) to form the image of the surface of asteroidonto a field stop which included 4 milliradian angular region of the image.Light passes through the first OAP to the second to re-collimates and set forththe Focal Plane Assembly. With each detector sees the same spatial region and othersin the array see at different wavelengths, the spectrum will be got with singlemeasurement. It is different from other wedged filter spectral imagers whosespectrum is built up over several different frames.Fig. 2. Reuter, D.C.

, et al. “The OSIRIS-REx Visible and InfraRedSpectrometer (OVIRS): Spectral Maps of the Asteroid Bennu.” CornellUniversity Library, Cornell University Library, 30 Mar. 2017,arxiv.org/abs/1703.

10574.Figure2 is the model ofthe OVIRS Optics Box exterior. This part is mainly to control temperature andseparate titanium flexures. The First stage radiator will cool down thetemperature of the second stage, then the inflight temperature of the wholeoptic box will be from range 120k to 150k. While remaining in low temperature,the thermal load on the focal plane will decrease.Fig.

3. Reuter, D.C., et al.

“The OSIRIS-REx Visible and InfraRedSpectrometer (OVIRS): Spectral Maps of the Asteroid Bennu.” CornellUniversity Library, Cornell University Library, 30 Mar. 2017, arxiv.org/abs/1703.10574. Figure 3 is a model ofthe interior of the box. The first mirror has an 80-mm aperture and a focallength of 350mm.

Image will form on field stop from the primary aperture orsolar calibrator aperture. The field stop is a 1.4mm circular aperture that letlight pass to the second mirror from a 4 milliradian angle.

Light will travelto the focal plane which is 150 mm from field stop and eventually, the angularspread of light will be 7 milliradian.Also, all the equipmenton OVIRS will pass through a Calibration Test before launch and during flight.In order to monitor the calibration during flight, OVIRS used solar calibrationaperture to access the stability of the system which is independent of otherdevices onboard.

The input will be point to the sun and the solar radiance willstrike the wire system near the focal plane. The mesh scatters and creates arelatively flat illumination pattern on entire focal plane. In figure 3,filament Calibrator and Blackbody Calibrator will monitor the calibrationfrequently. DataCollected and ResultsThe mission is still inprogress. It will reach Bennu is 2018 and return with data in 2023.

So wehaven’t got the data collected by OVIRS on Bennu yet.But why we choose Bennuover 500000 known asteroids in the solar system? First, for a mission likeOSIRIS-REx that investigate a near earth object, asteroids will be chosen from1.6 AU to 0.8 AU. When OSIRIS-REx’s asteroid selection begun in 2008, there areonly 192 asteroids that meet the requirements. Second, asteroid rotates fasterif they have small diameters. If it spins too fast, the loose material will beejected.

The target asteroid has to have a diameter larger than 200m for aspacecraft to safely land and gather enough data on it. This limits the 192asteroids to only 26. Third, Bennu is one of the most primitive asteroids thatare carbon rich and has stayed the same since they first form. Bennu contains alot of organics, volatiles and other material that have been the origins oflife on earth. Studying Bennu will benefit a lot with our understanding of theorigins of life. Only 5 asteroids of the 26 is carbon rich and primitive andBennu is one of it. Bennu has 500-meter diameter which is safe for spaceship toland, and it has an orbiting period of 436.604 days and it comes close to earthevery 6 years.

This gives us a high chance of discovering Bennu and that is whyBennu became the ideal asteroid for OSIRIS-REx.Fig. 4. “WHYBENNU?” OSIRIS-Rex Asteroid Sample Return Mission, NASA, www.asteroidmission.org/why-bennu/.  Historyand Development of OVIRSOVIRS is designed to belong-lasting and stable, reducing a lot of risk of malfunction. First, it hasto be at very low temperature to produce the best data, but temperature inspace varies a lot.

If OVIRS is heated up, there will be more thermal radiationand scattered light to interfere with the data. Scientists anodized theinterior coating of the spectrometer which increases resistance to corrosion ofthe metal. It also reduces the scattered light to stabilize environment ofOVIRS observation.

Another big threat iswater. As OVIRS will be searching for water in the surface, any water thatcomes in the instrument will damage the results. Even if the instrument avoiddirect contact with water, OSIRIS-REx may be affected by accumulating moisturewhile on the launch pad in Florida. In order to solve this, scientists willturn on heaters to eliminate water’s existence.ConclusionAlthough the mission isstill in progress, the design of OVIRS for OSIRIS-REx mission made a greatexample for detecting material and organics outside earth.

OVIRS has a set ofoptics to feed the focal plane which gives us spectral range of 0.4 to 4.3?m. The spectral data will return toEarth and bring scientists information of minerals, chemicals and organics,OVIRS will give us a detailed information including composition, thermalcharacteristics and so on, helping scientists learn more about the environmentin Bennu and maybe build a connection between Bennu and the primitivedevelopment of Earth.   WorkCitedD.C., Reuter, et al. “The OSIRIS-REx Visible and InfraRedSpectrometer (OVIRS): Spectral Maps of the Asteroid Bennu.

” CornellUniversity Library, Cornell University Library, 30 Mar. 2017, arxiv.org/abs/1703.

10574.Hille, Karl. “NASA to Map the Surface of an Asteroid.” NASA,NASA, 25 July 2016,www.nasa.gov/feature/goddard/2016/nasa-to-map-the-surface-of-an-asteroid.Jianing ZhangProfessor PommierSIO 125 January 2018 The OSIRIS-RExVisible and Infrared Spectrometer (OVIRS): Osiris-REX – AsteroidsFig.

0. NASA,et al. “OSIRIS-REx Technology: OVIRS.” NASA, NASA, 25 July 2016,svs.gsfc.nasa.gov/12309.

OSIRIS-REx is the thirdmission of NASA’s New Frontiers Program conducted by NASA’s Marshall SpaceFlight Center in Huntsville. The spaceship is built in Lockheed Martin SpaceSystems in Denver and OSISRIS-REx sicence Processing and Operations Center areat the University of Arizona, NASA’s Goddard Space Flight Center in Greenbelt.The instrument, OSRIS-REx Visible and infrared Spectrometer (OVIRS) will bediscussed in this report.Purpose& Scientific QuestionsIn the mission of sendingOSRIS-REx spacecraft to an asteroid Benuu that is rich of carbon material,scientists are hoping to find the origins of life in it.

They built theOSRIS-REx Visible and infrared Spectrometer (OVIRS) to look at asteroid Benuu’sspectral signature to detect minerals and organics. It breaks down light intoseparate individual wavelength packets in order for the scientists to analyzefrom the details of spectra to tell which material they are looking for. OVIRSwill work along with another instrument, the Thermal Emission Spectrometer(OTES). With information collected by OVIRS and OTES, scientists will alsostudy the Yarkovsky effect, which is how surface heating and cooling willaffect Bennu’s orbit.

 Mechanismsof InstrumentsOVIRS is a spectrometerequipped with a 4-mrad field of view providing wavelength range of 0.4 – 4.3um.

It has a wedged two-dimensional spectral filter (linearly variable, LVF)that could detect varies of substances. In LVF, wavelength of the transmittedlight will wary in one dimension. The filter segments will be put on anassembly placed over the detector. It has a spectral resolution defined asresolving power, R. Resolving Power Spectral Range(?m) R>= 125 0.4 to 1.1 R>= 150 1.

1 to 2.0 R>= 200 2.0 to 4.3 R>= 350 2.9 to 3.6  With this resolution,OVIRS could provide data of many mineral and molecular components such assulfates, oxides, canbonates, silicates, water and many organic species.

Itwill provide spectral data for the asteroid, spectral maps with 20m resolution.It will provide two spectral samples for each spectral resolution element tomake a full use of it.Fig. 1. Reuter, D.C., et al. “The OSIRIS-REx Visible and InfraRedSpectrometer (OVIRS): Spectral Maps of the Asteroid Bennu.

” CornellUniversity Library, Cornell University Library, 30 Mar. 2017,arxiv.org/abs/1703.10574.The shape of graph wasdetermined for the filter focal plane assembly with multi-order grating. Thus,it could generate a table of wavelength and resolving power.

Figure 11 shows anexample of the readout of LVF segments with the output of a gratingmonochromator. The three peaks matched to order of six to four of 4 ?m grating. Two lines shows theprogress of changing grating setting to pass through a spectral element…Wecould see from data of the instrument and determine that the line shape isGaussian.OVIRS is equipped with anoff-axis parabolic mirror(OAP) to form the image of the surface of asteroidonto a field stop which included 4 milliradian angular region of the image.Light passes through the first OAP to the second to re-collimates and set forththe Focal Plane Assembly. With each detector sees the same spatial region and othersin the array see at different wavelengths, the spectrum will be got with singlemeasurement.

It is different from other wedged filter spectral imagers whosespectrum is built up over several different frames.Fig. 2. Reuter, D.C., et al.

“The OSIRIS-REx Visible and InfraRedSpectrometer (OVIRS): Spectral Maps of the Asteroid Bennu.” CornellUniversity Library, Cornell University Library, 30 Mar. 2017,arxiv.

org/abs/1703.10574.Figure2 is the model ofthe OVIRS Optics Box exterior. This part is mainly to control temperature andseparate titanium flexures. The First stage radiator will cool down thetemperature of the second stage, then the inflight temperature of the wholeoptic box will be from range 120k to 150k. While remaining in low temperature,the thermal load on the focal plane will decrease.

Fig. 3. Reuter, D.C., et al.

“The OSIRIS-REx Visible and InfraRedSpectrometer (OVIRS): Spectral Maps of the Asteroid Bennu.” CornellUniversity Library, Cornell University Library, 30 Mar. 2017, arxiv.org/abs/1703.10574. Figure 3 is a model ofthe interior of the box.

The first mirror has an 80-mm aperture and a focallength of 350mm. Image will form on field stop from the primary aperture orsolar calibrator aperture. The field stop is a 1.4mm circular aperture that letlight pass to the second mirror from a 4 milliradian angle. Light will travelto the focal plane which is 150 mm from field stop and eventually, the angularspread of light will be 7 milliradian.Also, all the equipmenton OVIRS will pass through a Calibration Test before launch and during flight.In order to monitor the calibration during flight, OVIRS used solar calibrationaperture to access the stability of the system which is independent of otherdevices onboard.

The input will be point to the sun and the solar radiance willstrike the wire system near the focal plane. The mesh scatters and creates arelatively flat illumination pattern on entire focal plane. In figure 3,filament Calibrator and Blackbody Calibrator will monitor the calibrationfrequently. DataCollected and ResultsThe mission is still inprogress. It will reach Bennu is 2018 and return with data in 2023. So wehaven’t got the data collected by OVIRS on Bennu yet.

But why we choose Bennuover 500000 known asteroids in the solar system? First, for a mission likeOSIRIS-REx that investigate a near earth object, asteroids will be chosen from1.6 AU to 0.8 AU.

When OSIRIS-REx’s asteroid selection begun in 2008, there areonly 192 asteroids that meet the requirements. Second, asteroid rotates fasterif they have small diameters. If it spins too fast, the loose material will beejected. The target asteroid has to have a diameter larger than 200m for aspacecraft to safely land and gather enough data on it.

This limits the 192asteroids to only 26. Third, Bennu is one of the most primitive asteroids thatare carbon rich and has stayed the same since they first form. Bennu contains alot of organics, volatiles and other material that have been the origins oflife on earth. Studying Bennu will benefit a lot with our understanding of theorigins of life. Only 5 asteroids of the 26 is carbon rich and primitive andBennu is one of it. Bennu has 500-meter diameter which is safe for spaceship toland, and it has an orbiting period of 436.604 days and it comes close to earthevery 6 years.

This gives us a high chance of discovering Bennu and that is whyBennu became the ideal asteroid for OSIRIS-REx.Fig. 4. “WHYBENNU?” OSIRIS-Rex Asteroid Sample Return Mission, NASA, www.asteroidmission.org/why-bennu/.  Historyand Development of OVIRSOVIRS is designed to belong-lasting and stable, reducing a lot of risk of malfunction.

First, it hasto be at very low temperature to produce the best data, but temperature inspace varies a lot. If OVIRS is heated up, there will be more thermal radiationand scattered light to interfere with the data. Scientists anodized theinterior coating of the spectrometer which increases resistance to corrosion ofthe metal. It also reduces the scattered light to stabilize environment ofOVIRS observation.

Another big threat iswater. As OVIRS will be searching for water in the surface, any water thatcomes in the instrument will damage the results. Even if the instrument avoiddirect contact with water, OSIRIS-REx may be affected by accumulating moisturewhile on the launch pad in Florida. In order to solve this, scientists willturn on heaters to eliminate water’s existence.ConclusionAlthough the mission isstill in progress, the design of OVIRS for OSIRIS-REx mission made a greatexample for detecting material and organics outside earth. OVIRS has a set ofoptics to feed the focal plane which gives us spectral range of 0.4 to 4.3?m.

The spectral data will return toEarth and bring scientists information of minerals, chemicals and organics,OVIRS will give us a detailed information including composition, thermalcharacteristics and so on, helping scientists learn more about the environmentin Bennu and maybe build a connection between Bennu and the primitivedevelopment of Earth.   WorkCitedD.C., Reuter, et al. “The OSIRIS-REx Visible and InfraRedSpectrometer (OVIRS): Spectral Maps of the Asteroid Bennu.

” CornellUniversity Library, Cornell University Library, 30 Mar. 2017, arxiv.org/abs/1703.10574.Hille, Karl. “NASA to Map the Surface of an Asteroid.” NASA,NASA, 25 July 2016,www.nasa.gov/feature/goddard/2016/nasa-to-map-the-surface-of-an-asteroid.

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