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Spectroscopic observations of the Hayabusa reentry are presented as obtained by an instrument combining Fabry- Perot interferometry and classical optical emission spectroscopy. The instrument was deployed onboard NASA's DC- 8 airborne laboratory as part of the Hayabusa Reentry Airborne Observation Campaign led by NASA, in close collaboration with Japan Aerospace Exploration Agency. The covered wavelength range in the low-resolution mode is from 738.4 to 852.1 nm with the aim to acquire simultaneously the neutral atomic oxygen triplets at 777 and 844 nm and the nitrogen lines at 746 and 821 nm. The high-resolution mode reaches a wavelength resolution of Δλ = 0.01 nm. The intention of this instrument was to measure the translational temperature of the neutral atoms in the plasma flow ahead of the Hayabusa capsule. Air plasma emissions were detected at high resolution, but not at high enough signal to noise to measure the line width with sufficient accuracy. As expected, the measurements demonstrate the absence of significant pressure broadening in the lines compared with plasma wind-tunnel conditions [ABSTRACT FROM AUTHOR]

The 1069 nm line of atomic carbon was detected in radiation emitted during the 15 January 2006 reentry of the Stardust sample return capsule. In time-averaged data, the corresponding weaker lines in the range of 960-966 nm were also present. The spectra covered the wavelength range from 930 to 1075 nm at a spectral full-width-at-half-maximum resolution of 1.6 nm. The integrated 1069 nm line intensity decreased from 737 ± 44 W/m²/nm/sr at 80.7 km altitude (09:57:16.5 Universal Time) to 432 ± 44 W/m²/nm/sr at 70.9 km altitude (09:57:24.5 Universal Time). At the same time, the 1011 nm blend of nitrogen lines increased from 2110 ± 29 to 5378 ± 42 W/m²/nm/sr. Absolute calibration errors add to these values a systematic uncertainty of about 20%. The capsule's heat shield consisted of a phenol-impregnated carbon ablator. Hence, the intensity of the carbon-atom line emission is a measure of the ablation rate during descent, but it also depends on the details of carbon-atom ablation and the excitation in the shock layer. [ABSTRACT FROM AUTHOR]

During entry of the Stardust sample return capsule, measurements of the radiation emitted from the shock-heated flow were obtained with a number of instruments. These instruments viewed the sample return capsule from an airplane located several hundred kilometers from the vehicle. The present study analyzes the radiation generated at two different high-altitude conditions. The flowfields are simulated using both continuum (computational fluid dynamite) and particle (direct simulation Monte Carlo) methods. The flow solutions provide input to a nonequilibrium radiation model to compute line-of-sight spectra that are compared with high-resolution data taken with the Echelle spectrograph during the Stardust entry. Comparisons between simulation and measurements are presented fur air spectral features and for metal atomic lines believed to originate from evaporation of the vehicle surface. The comparisons make it possible to identify specific aspects of the air chemistry modeling that require further work. In addition, analysis of the metal spectra provides insight into the likely sources of these impurities. [ABSTRACT FROM AUTHOR]

The radiation emitted by the Stardust sample return capsule during reentry into Earth's atmosphere on 15 January 2006 was measured with a staring airborne intensified camera, equipped with an objective transmission grating. The instrumental setup was designed to provide low-resolution spectra of the capsule's radiation, even if other instruments would fail in tracking the object. Spectra were recorded at the video frame rate of 30 Hz. The spectra covered the range of 380-860 nm, with a dispersion of 2.3 nm/pixel and a full-width-at-half-maximum resolution of 7 nm. Fully calibrated results, to an absolute precision of ~17%, are presented for the time period from 09:57:17 to 09:57:43 Coordinated Universal Time, averaged over periods of 1 s. The data provided records of the CN band intensity detected throughout flight (unsaturated), the continuum emission (partially saturated), and the shock plasma emissions of oxygen and nitrogen during peak heating (partially saturated). A spectrum of wake radiation is also presented. [ABSTRACT FROM AUTHOR]

The 15 January 2006 reentry of the Stardust Sample Return capsule was photographed from 11.2-km altitude onboard NASA's DC-8 Airborne Laboratory in a series of brief 1/320 s exposures with a Nikon D70 digital still camera. The entry was detected from 09:57:13.5 to 09:57:53.5 UTC. Other instruments have demonstrated that most of the observed broadband flux is due to gray body radiation from the hot surface of the thermal protection system, except in the very beginning when strong emission lines of zinc from an ablating paint layer contributed significantly to the blue band. The measured flux in the green band was used to measure the surface-averaged temperature variation during flight, and the corresponding flux in the blue and red bands were used to verify the expected wavelength dependence of the gray body emission. [ABSTRACT FROM AUTHOR]

The descent of the Stardust Sample Return Capsule on 15 January 2006 was observed with an intensified high-frame-rate slitless spectrograph, which was operated in staring mode. Spectra were recorded at 300 frames per second from 09:57:47 to 09:57:57 UTC (Coordinated Universal Time), around the time of peak deceleration of the capsule. At this time, the spectra contained continuum emission from the hot surface and appeared to be featureless otherwise, with the exception of the telluric absorption caused by molecular oxygen in the atmosphere between the capsule and the observer. By averaging all spectra together, however, it was possible to bring out weak emission lines of oxygen and potassium over the time frame 09:57:51-54 UTC and sodium emission during 09:57:48-51 UTC. The spectral sequence was analyzed for signs of variation in the total emission from a possible wobbling of the capsule at periods higher than the spin rate. No such variation was observed above the detection threshold of 5° amplitude in the line of sight. [ABSTRACT FROM AUTHOR]

During the 2006 Stardust Sample Return Capsule entry observing campaign, the highest spectral resolution data gathered onboard NASA's DC-8 Airborne Laburatory was measured with a fixed-mounted slitless cooled charge-coupled-device spectrograph, called ASTRO. Spectra were recorded around the time of peak heating ~09 : 57 : 33 Coordinated Universal Time (UTC) on 15 January. The data covered three 0.8-second time intervals centered on 09:57:32.5, 34.4 and 36.3 s (±0.5 s) UTC, when the capsule was at an altitude of 60 and 210 kill from the spectrometer. The ohserved spectrum was a composite of first-, second-, and third-order emissions. The first-order spectrum contained only continuum emission. Second-order emissions included the 615 nm atomic line of oxygen; third-order emissions included the CN violet 0-0 band, the isoelectric N2+ band, and two Ca+ atomic lines. The Ca+ lines had an instrumental full-width at half-maximum of 0.15 ± 0.01 nm. The CN violet baud contour measured vibrational and rotational excitation temperatures of Tv = Tr = 8,000 ± 1,000 K, if self-absorption is neglected. [ABSTRACT FROM AUTHOR]

The 320-460 nm wavelength emission of the Stardust Sample Return Capsule's reentry in Earth's atmosphere was observed remotely with an intensified slitless spectrograph, which recorded spectra at a video rate of 29.97 frames/s. The spectral response remained constant during the full range of recovery, with only motion blurring from imperfect guiding contributing to small variations in detection response. The data are well suited for evaluating the temporal variation of the intensity of the various light-emitting components. A line of zinc identifies the period when a layer of ZnO pigment containing thermal protection paint was ablated. Ca+ emission was more intense during (and just following) the ablation of this zinc, but present throughout flight. Shock emission from nitrogen is no longer detected shortly after peak heating. The data are dominated by strong molecular band emission from the radical CN. The CN band intensity is thought to be proportional to the carbon ablation rate from the heat shield. Corrected for distance, the CN band intensity peaked early in flight, before peak heating, followed by an exponential decrease through peak heating. [ABSTRACT FROM AUTHOR]

Spectroscopic observations of the 2006 Stardust Sample Return Capsule entry are presented, obtained by means of a slitless miniature echelle spectrograph onboard NASA's DC-8 airborne laboratory. The data cover the wavelength range from 336 to 880 nm, at 0.14-0.9 nm resolution, and were obtained during the time interval when radiative heating was most important. The data contain a broadband continuum, presumably from the hot heat-shield surface, shock-layer air plasma emissions of N, O, and N2+, and atomic hydrogen and CN molecular band emission from the ablating heat-shield material, a form of phenol-impregnated carbon ablator. Early in flight, there were also atomic line emissions of Zn, K, Ca+, and Na, presumably from a white Z-93P paint applied to the top of the phenolimpregnated carbon ablator. At each moment along the trajectory, the whole spectrum was recorded simultaneously, but broken into smaller segments. Key issues addressed in the data reduction and calibration are described. The interpretation of these data was given elsewhere. [ABSTRACT FROM AUTHOR]

As part of the 2010 airborne observational campaign for the Hayabusa capsule reentry, a system of four colocated cameras was deployed to track and measure the spacecraft fragmentation and sample return capsule descents. These instruments included an intensified video camera for narrow-field tracking, an intensified video camera for visible and near-infrared spectral measurements from 400 to 900 nm, and a near-infrared spectrograph for high-resolution measurements from 980 to 1080 nm. The latter was configured to monitor the spectral evolution of capsule emissions during descent, seeking evidence of possible carbon signatures due to ablation of the heat shield. The data complement previous Stardust capsule observations in which distinct 1069 nm emission signatures were measured, likely associated with carbon ablation from the Phenolic Impregnated Carbon Ablator heat shield. The Hayabusa capsule spectra also exhibited 1069 nm line emissions, appearing intermittently at ~13 : 52 : 05, persisting from approximately 13:52:10 to 13:52:20 as the capsule approached peak heating, and weakening to undetectable levels after ~13 : 52 : 20. Continuum emission and nitrogen line emissions were detected simultaneously. The evolutions of these signatures over the course of reentry are investigated, in comparison with model predictions and complementary campaign data. [ABSTRACT FROM AUTHOR]

Quantitative time-resolved irradiance measurements were obtained of the Hayabusa Sample Return Capsule's entry on 13 June 2010, as measured from a 12.6 km altitude with the Australian Ultraviolet Spectrograph instrument on board the NASA DC-8 Airborne Science Laboratory, jointly managed by the NASA Airborne Science Program and the National Suborbital Education and Research Center. The NASA DC-8 Airborne Science Laboratory was stationed just outside of the landing site at the Woomera Test Range in Australia. The measurements were calibrated against National Institute of Standards and Technology traceable standard calibration lamps on the tarmac at NASA Dryden Aircraft Operations Facility, operated by NASA Dryden Flight Research Center, and at NASA Ames Research Center. The recorded spectra cover the wavelength range from 300 to 470 nm over the duration from 13:52:02.5 until 13:52:33.5 coordinated universal time. The spectra show shock emission from singly ionised molecular nitrogen (N2+), as well as several ablation products from the heat shield material: cyanogen radical, calcium, and aluminium. In addition, the high-temperature tail of gray-body emission is observed to enter the wavelength range after 13:52:13 coordinated universal time. These data were evaluated in terms of the temporal evolution of the capsule's stagnation temperature and emissions within the cyanogen radical and (N2+) manifolds. A peak in the irradiance within the wavelength band from 365 to 392 nm was registered at approximately 13:52:07 coordinated universal time and elevated levels ofirradiance within the combined cyanogen radical and (N2+) manifolds were subsequently registered at about 13:52:20 coordinated universal time. An apparent maximum capsule temperature close to 3050 K was found at around 13:52:23 coordinated universal time, consistent with apparent capsule temperature values deduced using other instruments. [ABSTRACT FROM AUTHOR]

Predicted shock-layer emission signatures during the reentry of the Japanese Hayabusa capsule are presented and compared with flight measurements conducted during an airborne observation mission in NASA's DC-8 Airborne Laboratory. For selected altitudes at 11 points along the flight trajectory of the capsule, lines of sight were extracted from flowfield solutions computed using the high-fidelity computational fluid dynamics code Dplr. These lines of sight were used as inputs for the line-by-line radiation code Neqair, and emission spectra of the air plasma were computed in the wavelength range from 300 to 1600 nm, a range that covers all of the different experiments onboard the DC-8. In addition, the computed flowfield solutions were postprocessed with the material thermal response code Fiat, and the resulting surface temperatures of the heat shield were used to generate thermal emission spectra based on Planck radiation. Both spectra were summed and integrated over the flowfield. The resulting emission at each trajectory point was propagated to the DC-8 position and transformed into incident irradiance to be finally compared with experimental data. [ABSTRACT FROM AUTHOR]

Hypersonic flowfield and radiation analyses are performed before and after flight to study the physical conditions experienced by the automated transfer vehicle Jules Verne during reentry before breakup. Results are compared to those obtained with a miniature Echelle spectrograph operated from an airborne platform, measuring the flux density of atomic line emissions from oxygen and nitrogen, as well as many metals. Molecular emissions from CN and AIO are also detected. The vehicle lost its solar panels at 86 km and first broke up at 75 kin. The main cargo cabin held together until 68 km. Postflight analyses focus on altitudes of 86, 75, and 68 km. A first analysis includes only + air species, correctly predicting the observed oxygen and nitrogen atomic line intensities. N band emission is systematically overestimated by at least a factor of 20, indicating a need for revision of the radiation model for this system. A second analysis includes blowing of metals (aluminum, sodium, potassium, and magnesium) from the vehicle surface. The blowing rates are inferred by requiring the computed and measured emissions to match. Magnesium and aluminum originate from ablation of structural elements, while sodium and potassium may have originated as impurities in paint. [ABSTRACT FROM AUTHOR]

Observations were made during the reentry of the Stardust sample return capsule on 15 January 2006 in order to calibrate the level of radiation from the capsule surface, from the bow shock, and from its wake. A sensitive cooled charge-coupled device camera was used, equipped with a grating to simultaneously record the first-order spectrum of the capsule and that of the background stars. The radiation of the capsule was dominated by the graybody radiation from the hot surface. This graybody radiation was calibrated against the known radiation of background stars. The purpose of this calibration was to provide a cross check for other instruments participating in the airborne Stardust Entry Observing Campaign. In addition, eight short-exposed images were obtained that show the development of billowing and the distortion induced by winds. [ABSTRACT FROM AUTHOR]

The reentry of the Stardust sample return capsule was captured by several optical instruments through an observation campaign aboard the NASA DC-8 airborne observatory. Flow environments obtained from computational fluid dynamics solutions are loosely coupled with material response modeling to predict the surface temperature and the observed continuum emission of Stardust throughout the reentry. The calculated surface temperatures are compared with the data from several spectral instruments onboard the airborne observatory, including the ECHELLE (echelle-based spectrograph for the crisp and high efficient detection of low light emission) camera and conventional spectrometer in Czerny-Turner configuration. The ECHELLE camera recorded spectral intensity at a period in the trajectory before peak heating. The graybody curves corresponding to the average and area-averaged surface temperatures predicted by the computational fluid dynamics and material response coupled simulation have excellent agreement with the recorded data at altitudes lower than 74 km. At these altitudes, the computational fluid dynamics and material response coupling agrees with the surface temperature to within 50 K. The computational fluid dynamics calculation without the material response modeling overestimates surface temperatures because it does not take into account such things as ablation. The overprediction of the computational fluid dynamics and material response simulated surface temperature early in the trajectory coincides with high-emission intensity lines corresponding to thermal paint products. The presence of paint on the heat shield could have contributed to the lower observed surface temperatures and could explain the overprediction by the simulated data, which does not account for the paint. The average surface temperatures resulting from the spectrometer in Czerny-Turner configuration telescope analysis agree to within less than 5% with the average surface temperatures predicted by the material response. This observation period included the point of peak heating. The calculated flux based on the surface temperature agrees well with the observed flux. Surface temperature is one of the critical parameters used in the design of thermal protection systems, because it is an indicator of material performance. The coupled computational fluid dynamics and material response approach employed in the present analysis increases confidence for future missions such as the crew exploration vehicle Orion. [ABSTRACT FROM AUTHOR]

A high-fidelity three-dimensional approach is developed to simulate emission signatures from the shock layer around the Stardust sample return capsule at several points on its best-estimated trajectory. Calculations are performed with various gas chemistry, thermodynamic, and radiation models. Results are compared against calibrated imaging data acquired by a slitless echelle spectrometer. The present analysis is based on flowfields computed without the inclusion of ablation products, and the comparison is focused on radiation from atomic oxygen and nitrogen lines. The purpose is to apply and improve, if necessary, the current models used in nonequilibrium atmospheric entry simulations. [ABSTRACT FROM AUTHOR]