Data Set Information
DATA_SET_NAME REDDY MAIN BELT ASTEROID SPECTRA V1.0
DATA_SET_ID EAR-A-I0046-3-REDDYMBSPEC-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : All spectral observations were obtained using the SpeX instrument on the NASA IRTF in low-resolution prism mode. Observations were made remotely and in classical mode on site. SpeX in low resolution mode has resolving powers of R~100 across the wavelength region from ~0.7 to 2.5 microns. An infrared guider is available to guide on calibration stars (sidereal rates) and asteroids (non-sidereal rates). The main spectrograph uses a 1024x1024 Aladdin 3 InSb array and the guider uses a 512x512 Aladdin 2 InSb array [RAYNERETAL2004]. Low-resolution spectrographs like SpeX are ideal for resolving broad absorption features produced by abundant mafic minerals like olivine and pyroxene that make up many asteroid surface assemblages. The low resolution prism mode also helps in obtaining spectra with higher signal-to-noise-ratios (SNR) and asteroids as faint as Vmag~17.5 are routinely observed. Spectral observations for this data set were made by taking nodded spectral image pairs of the asteroid, local standard star (for telluric correction), solar-analog stars, and calibration flat-field and argon arc-lamp images. The placement of these stellar observations, temporally and spatially on the sky, in relation to the asteroid is important for producing good quality spectra. If the atmosphere over Mauna Kea is stable throughout the observing run (photometric), then the log of the flux (apparent magnitude) of the object will decrease linearly with increasing airmass. Hence, all objects are typically observed at airmasses less than 1.5, which corresponds to a zenith angle of less than 50 degrees. However, if the atmosphere is unstable over Mauna Kea, whether due to an orographic cap cloud or rapid variability of water vapor content, it often produces a non-linear magnitude- airmass relationship. Local (or extinction) standard stars close to the asteroid are observed to correct for the terrestrial atmospheric water vapor features. Generally, the greater the distance between the local standard star and the asteroid, the poorer the monitoring of the sky conditions for the asteroid. During a typical observing run, a local standard star with spectral properties similar to our Sun (i.e., G-type, main sequence stars) is paired with an asteroid and is observed over a wide airmass range that bracket the airmass range of the asteroid observations. Solar analog stars are observed to remove the solar continuum from the asteroid spectrum. At least two solar analog stars should be observed each night to eliminate the possibility of systematic errors that may be present in a single solar analog star spectrum. SpeX prism data was reduced using the IDL-based Spextool provided by the NASA IRTF [CUSHINGETAL2004]. The steps followed in the reduction process include: (1) sky background removal by subtracting the image pairs, (2) flat-fielding, (3) cosmic ray and spurious hit removals, (4) wavelength calibration, (5) division of asteroid spectra by the spectrum of the solar analog star, and (6) co-adding of individual spectra. NOTE: Definitions for keywords which may appear in the labels: IMAGE_COUNT is the number of individual observations which have been combined to produce the final spectrum. APPARENT_MAGNITUDE is the apparent V magnitude of the target. FILTER_NAME (always V) is the filter of the APPARENT_MAGNITUDE. STAR_NAME is the name of the solar analog star used to reduce the observation. PHASE_ANGLE, SOLAR_DISTANCE, and AIRMASS all refer to the target. Plots with all the NIR spectra are provided in a pdf file located in the document directory. Numbers in the plots refer to the asteroid number. Error bars are not included in the plots.
DATA_SET_RELEASE_DATE 2016-06-02T00:00:00.000Z
START_TIME 2001-03-11T12:00:00.000Z
STOP_TIME 2012-06-24T06:15:11.000Z
MISSION_NAME SUPPORT ARCHIVES
MISSION_START_DATE 1965-01-01T12:00:00.000Z
MISSION_STOP_DATE 2015-01-01T12:00:00.000Z
TARGET_NAME 317 ROXANE
20 MASSALIA
12 VICTORIA
1124 STROOBANTIA
66 MAJA
951 GASPRA
182 ELSA
105 ARTEMIS
192 NAUSIKAA
1830 POGSON
2045 PEKING
138 TOLOSA
442 EICHSFELDIA
434 HUNGARIA
2 PALLAS
2014 VASILEVSKIS
1929 KOLLAA
1145 ROBELMONTE
741 BOTOLPHIA
389 INDUSTRIA
87 SYLVIA
44 NYSA
51 NEMAUSA
2011 VETERANIYA
306 UNITAS
101 HELENA
1 CERES
504 CORA
872 HOLDA
502 SIGUNE
1717 ARLON
704 INTERAMNIA
1883 RIMITO
385 ILMATAR
113 AMALTHEA
809 LUNDIA
255 OPPAVIA
273 ATROPOS
64 ANGELINA
233 ASTEROPE
482 PETRINA
9 METIS
256 WALPURGA
1251 HEDERA
84 KLIO
289 NENETTA
170 MARIA
37 FIDES
1284 LATVIA
45 EUGENIA
184 DEJOPEJA
472 ROMA
283 EMMA
121 HERMIONE
63 AUSONIA
1329 ELIANE
1626 SADEYA
308 POLYXO
403 CYANE
379 HUENNA
670 OTTEGEBE
130 ELEKTRA
569 MISA
858 EL DJEZAIR
56 MELETE
ASTEROID
663 GERLINDE
213 LILAEA
4 VESTA
22 KALLIOPE
470 KILIA
30 URANIA
419 AURELIA
762 PULCOVA
264 LIBUSSA
276 ADELHEID
41 DAPHNE
253 MATHILDE
1086 NATA
243 IDA
877 WALKURE
167 URDA
620 DRAKONIA
214 ASCHERA
458 HERCYNIA
349 DEMBOWSKA
863 BENKOELA
135 HERTHA
446 AETERNITAS
TARGET_TYPE ASTEROID
INSTRUMENT_HOST_ID OBS376T3
INSTRUMENT_NAME SPEX
INSTRUMENT_ID I0046
INSTRUMENT_TYPE IMAGER
SPECTROMETER
NODE_NAME Small Bodies
ARCHIVE_STATUS
CONFIDENCE_LEVEL_NOTE Confidence Level Overview : Uncertainties in spectral parameters for near-IR data are crucial for detecting and quantifying surface composition. The average wavelength resolution of the Spextool data is ~ 0.0035 microns. This is just due to spectral resolution based on the wavelength calibration. When spectra were combined the statistic used was the robust weighted mean. For this, Spextool makes use of a sigma clipping algorithm to identify outliers. The value at each pixel is then the weighted average of the good pixels and the uncertainty is given by the propagated variance. Uncertainties in the data arise primarily due to low SNR of the final average spectrum, incomplete correction of telluric absorption features, and variable sky/weather conditions. Data corresponding to asteroids (45) Eugenia, (213) Lilaea, (256) Walpurga, (308) Polyxo, (389) Industria, (442) Eichsfeldia, (1145) Robelmonte, (1284) Latvia, (1329) Eliane have error values much larger than might be expected given the scatter in the spectrum data points. The cause for these large uncertainties was not identified, but could be related to the small number of individual spectra that were combined to obtain the final spectrum. For these spectra the point-to-point scatter of the data provides a better estimate of the uncertainty associated with these measurements.
CITATION_DESCRIPTION Reddy, V. and Sanchez, J.A., Reddy Main Belt Asteroid Spectra V1.0. EAR-A-I0046-3-REDDYMBSPEC-V1.0. NASA Planetary Data System, 2016.
ABSTRACT_TEXT This data set contains low-resolution (R~150) near-infrared (0.7-2.5 microns) spectra of 90 main belt asteroids observed with the SpeX instrument on the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawai'i. This data set archives reduced, calibrated spectra of targets of opportunity observed from 2001 to 2012.
PRODUCER_FULL_NAME JUAN SANCHEZ
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