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James Webb Space Telescope
Science Operations Design Reference Mission

JWST SODRM Solar System Programs

TITLE: Martian Atmosphere

ID: 92010

GOAL:

While Mars continues to be the subject of reconnaissance missions (both orbital and landing), there remains a deficiency in the knowledge of the detailed diurnal cycles of various gasses and aerosols in the atmosphere. Current and planned probes are not capable of sampling multiple local times "i.e., local diurnal variation" on sub-seasonal time-scales for most of the Martian surface area; they are not Mars-synchronous, and are high inclination orbits. Furthermore, there are no planned Thermal-IR instruments for Mars.

While HST affords a look at the entire disk, the current instrumentation is insufficient to probe the thermal infrared. In addition, the orbital constraints on HST forbid prolonged, continuous. Monitoring of the atmospheric changes over Martian day.

JWST solves these problems with it's suite of instrument, and its L2 orbit, which enables the observatory to monitor the Martian atmosphere on timescales from a few minutes, to weeks with any cadence that is required by the observer. Here we use the NIRSpec and MIRI IFUs to obtain synoptic monitoring of gases, aerosols, and dust in the Martian atmosphere over the entire disk.

This program proposes to monitor over 2 consecutive Martian days (24.6 earth hours), 4 times during the Martian year. The four yearly epochs will coincide with important seasonal transitions where the atmosphere is undergoing significant heat load changes. It is necessary to monitor Mars for two full days in order to get full coverage of the Martian surface with both instruments, and a minimum interruption due to instrument change overheads.

OBSERVING TEMPLATE:

MIRI IFU Spectroscopy
NIRSpec IFU Spectroscopy

OBSERVATION DETAILS:

NIRSpec will be used to measure the strengths of ice features, which constrain particle size (aerosol components). CO and H2O will be measured. MIRI IFU observations can constrain:

  1. The dust particles size distribution via the ratio of 9.7μm/21μm silicate feature strength.
  2. The CO2, since the 15μm feature is optically thick

For both instruments, it will be necessary to form a mosaic to cover the entire face of Mars. The Mosaics are designed with 1/2 array overlap.

We select a 5x5 mosaic (with half-array offsets) to achieve full disk coverage for the shortest wavelengths of MIRI and for the NIRSpec IFU. In addition, we apply a 4-point (2x2) raster at each mosaic tile.

CONSTRAINTS:

Epochal observations need to be uninterrupted. Ideally, the NIRSpec and MIRI observations should be interleaved. Regardless, the NIRSpec and MIRI should be executed back-to-back. One possible problem with observing the planet for two full Martian days is the need to switch guide stars in order to track the planet.

PROGRAM COORDINATOR/DATE: D. C. Hines, M. Wolff/9 January 2012

For more information about this program refer to the latest version of the SODRM.


TITLE: Periodic Comets

ID: 92020

GOAL:

  1. Composition and Activity of Comets

    This program will study the composition and dynamics of dust and gas in the comae of 6 active comets using NIRSpec and MIRI. The NIRSpec data will be acquired through the 0.2 x 3.3" slit. Because those spectra will be dominated by reflected sunlight, spectra of an appropriate Solar- type spectroscopic standard star will be needed. These Solar calibration spectra will have an SNR significantly higher than those we expect to acquire on the comets, so that the comparison spectrum will not degrade the SNR of the cometary spectra.

    The MIRI data will be strongly dominated by thermal emission, so no Solar comparison spectrum will be needed for the LRS data. MIRI will also be used to make 10 μm maps of the coma and dust-trail structure. Each comet will be observed twice to sample activity at different phases in its orbit.

    NIRSpec medium resolution spectra (G235M, G395M) will be used to characterize broad emission lines from H2O, CO2 and organic molecules in the gas phase. These spectra will also be highly sensitive to the presence of water ice and silicates in the dust grains of the coma. Spectra, with the the 0.2 x 3.3" slit, will be taken of the region surrounding the comet nucleus to characterize the gas and dust composition before interactions with UV and chemical evolution have taken place, and also at a position offset from the nucleus to characterize the photo/chemical processes in the coma. These data will be dominated by reflected sunlight,

    NIRSpec high resolution spectra (G235H and using the 0.2 x 3.3" slit) will be used to measure abundances of higher-order organic molecules, and to measure the D-H ratio of the water in the coma. As with the medium resolution data, spectra will be acquired both on the nucleus and at an offset position.

    MIRI LRS data from 5-14 μm will be used to characterize the composition of the dusty component of the coma, and will be sensitive to the emission features of silicates, PAHs and other large organic molecules. The LRS data also provides sensitive constraints on the temperature of the dust, and its grain-size distribution. The LRS data will only be taken on the near-nucleus region of the coma.

    MIRI 10 μm maps, covering roughly 8' x 20', will be made of the coma and near-nucleus dust trail. The maps will reveal jet structures in the coma, providing constraints on the rotation state of the nucleus, and the dust production rate and velocity of ejection.

  2. Physical properties and possible activity of distant comet nuclei

    MIRI LRS spectra and 15 μm imaging of 18 periodic comet nuclei will be acquired while those objects are near their perihelia. Activity should be absent (all will be at distances > 6AU when observed). The data will be interpreted using thermal models, which will be fit to the LRS thermal spectra and the anchoring the 15 μm photometric point. The data will also provide very sensitive constraints on whether activity is truly absent. The 15 μm PSF will be examined for any evidence of extended emission, and the spectra will be sensitive to the presence of very small amounts of fine-grained dust, should there be any coma. Each comet will be observed twice to sample activity at different phases in its orbit.

TARGET(S):

Active-Comet Sample: 31P/Schwassmann-Wachmann_2
68P/Klemola
101P/Chernykh
200P/Larsen
231P/LINEAR-NEAT
232P/Hill
Distant-Nuclei Sample: 8P/Tuttle
27P/Crommelin
55P/Tempel-Tuttle
63P/Wild_1
93P/Lovas_1
97P/Metcalf-Brewin
99P/Kowal_1
126P/IRAS
134P/Kowal-Vavrova
140P/Bowell-Skiff
142P/Ge-Wang
151P/Helin
179P/Jedicke
192P/Shoemaker-Levy_1
195P/Hill
241P/LINEAR
242P/Spahr
248P/Gibbs
Solar Analog HD 129357 - G2V

OBSERVING TEMPLATE:

MIRI LRS Spectroscopy
MIRI Imaging

OBSERVATION DETAILS:

  1. Composition and Activity of Comets

    MIRI LRS - 10.2 hrs

    Each epoch of LRS observations will have the following characteristic.
    Two epochs will require 1.7 hrs. To observe all six comets will require 10.2 hrs

    MIRI 10 μm Imaging - 5.4 hrs

    We use a 5 point dither pattern with the shortest exposure per pointing. For each epoch this yields.
    Two epochs will require 0.9 hrs. To observe all six comets will require 5.4 hrs.

    NIRSpec Fixed-Slit - 19.2 hrs

    We use a two-position dither and 5 exposures at each dither. For each epoch, this yields: Two epochs will require 3.2 hrs. To observe all six comets will require 19.2 hrs.

  2. Physical properties and possible activity of distant comet nuclei MIRI LRS - 45.0 hrs

    Each epoch of LRS observations will have the following characteristic.
    Two epochs will require 2.5 hrs. To observe all six comets will require 45.0 hrs.

    MIRI 15 μm Imaging - 16.2 hrs

    We use a 5 point dither pattern with the shortest exposure per pointing. For each epoch this yields.
    Two epochs will require 0.9 hrs. To observe all six comets will require 16.2 hrs.

PARALLEL Observations possible (yes/no/pure parallel)?

In general parallels are not useful since these are moving targets.

COMMENTS:
The SNR for these objects was estimated by computing the surface brightness expected from the coma (assuming an optical depth of 10-4), converting that into an equivalent point-source flux, and adding the coma and nucleus contributions.

Here we estimated the SNR achieved on spectroscopic lines by computing the SNR just outside a line (longer and shorter wavelengths), and comparing that to the SNR in the core of the line.

PROGRAM COORDINATOR/DATE: D. C. Hines, J. Stansberry, W. M. Kinzel/23 December 2011

For more information about this program refer to the latest version of the SODRM.


TITLE: Bright Comets, Targets of Opportunity (ToO)

ID: 92030

GOAL:

Comets are the building blocks of the solar system and contain pristine samples of the early solar system debris cloud. Spectroscopic observations will allow determination of the comets' composition.

Sample and sky coverage: Assumed one comet, 134P/Kowal-Vavrova at three epochs between 2012.5 and 2013.5 when the comet is in the JWST field of regard. Each epoch will have a MIRI and NIRSPEC visit. The comets parameters were taken from the JPL DASTCOM database (JPL 2004a).

We will observe comets that are newly discovered as well as those in the main asteroid belt that flare unexpectedly. Multiple epochs are useful, but it is more important to monitor over a few day period to trace rotational changes.

NOMINAL ALLOCATION (hours):

105.8

TARGET(S):

Comets

OBSERVING TEMPLATE:

MIRI MRS-IFU
NIRSpec IFU
NIRCam Imaging

OBSERVATION DETAILS:

Each comet should be observed three times. The total time for this program could be reduced if we reduced the sightings to two, and could drop NIRCam.

Basis for exposure time estimates (S/N & brightness):

A S/N of about 10 is assumed. The JPL Horizons program (JPL 2004b) was used to produce ephemerides of the comets over the time range 2012.5 - 2013.5 and to determine when the comet was within the field of regard for JWST. It also produced an estimate of the nucleus visual magnitude, which was used to estimate the IR magnitudes. Conversions from (I, J, K) to AB magnitudes were from the ABmag calculator on the JWST web site.

NIRCam Imaging - 24.4 hrs

Time per single observations. This is repeated three times per comet, for five comets.

NIRSpec IFU Spectroscopy - 62.5 hrs

2x2 mosaic and 3-position dither at each location.
Time per single observations.
This is repeated three times per comet, for five comets.

MIRI IFU Spectroscopy - 18.9 hrs

CONSTRAINTS:

Moving targets

At least three sightings should be done per comet: one when comet is far away from Sun, and another when the comet has developed a large coma and tail.

PARALLEL Observations possible (yes/no/pure parallel)?

These are moving targets, so parallels are not appropriate.

PROGRAM COORDINATOR/DATE: D.C. Hines, J.Stansberry, C. Lisse/12 December 2011

For more information about this program refer to the latest version of the SODRM.


TITLE: Icy Dwarf Planets

ID: 92040

GOAL:

Beyond Neptune there are 4 dwarf planets (Pluto, Eris, Makemake and Sedna) with significant inventories of volatile ices on their surfaces. These ices give rise to organic molecules via UV photolysis and radiolysis by galactic cosmic rays. Haumea is also a dwarf planet, but is not currently known to possess any volatile ices. The physical state of the ices and the composition of the organics on these objects are of significant interest because these bodies are large enough to have retained nearly the entire inventory of material from which they accreted, because the volatile ices are mobile, moving in response to seasonal variations in insolation, and the ices also support the vapor-pressure atmospheres around these bodies. An important goal for JWST will be to make detailed studies of the composition of each object to determine what molecules are present on their surfaces (and in their atmospheres), measure isotopic compositions on each, and map the distribution of the constituents vs. longitude. JWST may also allow for the first detection of the low-temperature phase of solid N2 on one or more of these objects, for the first time, and determine whether N2 is present at all on Eris (where there is only indirect evidence for it).

The thermal state of the surfaces for each of these objects is also of interest, so MIRI 25μm photometry will be done to measure the thermal lightcurves for the brighter objects (for comparison with Spitzer and Herschel lightcurve data, and to measure secular changes related to seasonal cycles), and to measure the mid-IR thermal emission for the first time for the fainter objects.

Summary of observation requirements for dwarf planets:
We will use multiple observations in several cases to probe multiple longitudes. Estimated requirements below.
NIRSpec: SNR calculated at 1.5, 2.5, 4.3 μm for G140, G235, G395, respectively and is per resolution element.

 G140 G235 G395 Total
Object m_J Visits ExpTime SNR ExpTime SNR ExpTime SNR ExpTimeNote
Pluto 14.0 4 1200 300 3600 300 3600 150 5.3G395H
Eris 18.2 4 3600 100 14400 90 14400 75 36.0 
Make 16.9 2 7200 200 7200 120 7200 100 12.0 
Sedna 20.7 1 14400 60 14400 35 28800 15 16.0All medium res.
Haumea 17.0 1 7200 200 7200 130 7200100 8.0 
             Total: 77.3 hrs

Will want to sample specific longitudes on each object, but it isn't critical the data all be taken within ~1 rotation period. For simplicity, apply a timing constraint to each visit for each target.

MIRI:

Jy # 25.5 μm
Object F24 Visits ExpTime SNR Note
Pluto 5.0e-3 12 100 300 Rotational lightcurve
Make 1.1e-4 12 600 170 Rotational lightcurve
Sedna 7.7e-6 5 7200 4 Follow-on/sky subtraction
Haumea 2.2e-4 12 1800 60 Rotational lightcurve
             Total: 28.3 hrs

Flux densities derived from 45K BB, and normalized to 24μm flux density.

For simplicity, use follow-on constraints that space the observations about 12 hours apart. Actual constraints will depend on the object, but won't be vastly different than 12 hours. The first visit for each target should also include a timing constraint.

Specifics for each object:

  • Pluto (6.4 day period), but does not have to be contiguous. Because Pluto has such a long period, it makes sense to interleave the instruments over a two day period.
  • Eris we want four longitudes 1.08 days rotation. Make 2 visits over 24 hrs.
  • Sedna 10.3 hrs rotation period, one visit NIRSpec, so maybe 4 visits MIRI.
  • Haumea 4.7 hrs (rotation too fast for multiple longitudes... one visit).

TARGETS:

24μm flux in mJy
Vmag and F24 are for epoch c. June 2019
Jmag a wag from Vmag
NIRSpec integration times assume G2V normalized to Jmag

Object Vmag Jmag Rhelio Delta F24um
Pluto 14.4 14.0 33.9 34.6 5.0
Eris 18.8 18.2 96.0 95.1 1.0e-4
Makemake 16.9 16.9 52.652.7 0.11
Sedna 21.0 20.7 84.6 85.0 7.7e-3
Haumea 17.2 17.0 50.349.5 0.22

OBSERVING TEMPLATE:

MIRI Imaging
NIRSpec fixed-slit spectroscopy

PARALLEL Observations possible (yes/no/pure parallel)?

In general parallels are not useful since these are moving targets.

PROGRAM COORDINATOR/DATE: D. C. Hines, J. Stansberry/12 January, 2012

For more information about this program refer to the latest version of the SODRM.


TITLE: Solar System Ice Giants: Uranus & Neptune

ID: 92050

GOAL:

The ice giant planets of our solar system, Uranus and Neptune, are prime candidates for infrared imaging and spectroscopic observations with the James Webb Space Telescope (JWST). Their atmospheres, which are rich in hydrocarbons and seasonally varying clouds and storms, can be probed by JWST to explore their chemistry and thermal balance with unprecedented precision. Current ground-based observatories are unable to probe the atmospheres of ice giants (Uranus and Neptune) to large vertical depth or with sufficient accuracy because of terrestrial atmospheric absorption and high thermal background. Spatially resolved measurements of methane and ethane emission features in the upper atmospheres of Uranus and Neptune will help constrain the abundances of these compounds and the photochemistry involved in their formation. The abundances and variability of chemical species, including the confirmation of radicals thought to be involved in the hydrocarbon photolysis process, may be observed with JWST to more accurately characterize the atmospheric processes and formation of these planets.

NIRCam imaging, NIRSpec IFU spectroscopy, and MIRI IFU spectroscopy imaging will be obtained for both planets. Neptune is too bright for MIRI Imaging. These observations will be obtained with a cadence that will enable us to probe these atmospheres 4 times during their rotation periods (17.24 hours for Uranus and 16.11 hours for Neptune). The observation suite will be repeated at least 2 times per earth year to probe long-term variations.

NOMINAL ALLOCATION (hours):

168

TARGET(S):

Uranus
Neptune

OBSERVING TEMPLATE:

MIRI MRS-IFU
NIRSpec IFU
MIRI Imaging
NIRCam Imaging

OBSERVATION DETAILS:

All observations are taken 4 times to sample the latitudinal variations on the planet.

General Description of Exposure Time Calculations

We used the JWST exposure time calculator (ETC) to estimate exposure times of Uranus and Neptune in each observing mode based on flux values derived from existing IR spectra of both planets. We compared the exposure time estimates for wide and narrow-band imaging with the planetary rotation rates (17.24 hours for Uranus and 16.11 hours for Neptune) to determine the number of imaging filters and spectral resolution elements that may be sampled before significant planetary rotation occurs. Tables 1 and 2 provide a list of proposed exposure times with corresponding SNRs for Uranus and Neptune, respectively. Based on the observing plans provided in Tabke s 1 and 2, Uranus will rotate by 18.4° and Neptune will rotate by 6.4° if all observations are made in succession, assuming no overheads. Overhead estimates are not currently available, but if we assume ~50% efficiency for Uranus and ~10% efficiency for Neptune. Filters were selected for exposure time calculations based on filter bandwidth and spectral feature overlap.

Table 1 Example Uranus Exposure Time Calculations

Instrument

Filter

l (mm)

Feature (mm)

Exp. Time (s)

SNR

Total Time (s)

MIRI

MRS 1.c

6.49 - 7.76

CH4 : 7.5

245

20

1225

MIRI

MRS 3.a

11.47 - 13.67

C2 H6 : 12.3

135

20

675

MIRI

MRS 3.b

13.25 - 15.8

C2 H2 : 14.0

27.105

35

135.525

MIRI

F0770W

6.6 - 8.8

CH4 : 7.50

27.105

35

135.525

NIRSpec

R=2700

0.6 - 5.0

-

100

28

1000

Table 2 Example Neptune Exposure Time Calculations

Instrument

Filter

l (mm)

Feature (mm)

Exp. Time (s)

SNR

Total Time (s)

MIRI

MRS 1.c

6.49 - 7.76

CH4 : 7.15

27.105

215

81.315

MIRI

MRS 2.a

7.45 - 8.90

CH4 : 7.95

27.105

530

81.315

MIRI

MRS 3.a

11.47 - 13.67

C2 H6 : 12.25

27.105

480

81.315

NIRCam

F480M

4.6 - 5.0

CO: 4.7

10.6

430

53

NIRCam

F335M

3.18 - 3.52

H3+ : 3.4

10.6

290

53

NIRCam

F356W

3.12 - 4.0

CH4 : 3.5, 3.8

10.6

590

53

NIRSpec

R=2700

0.6 - 5.0

-

50

48

625

MIRI Imaging for Uranus - 25.6 hrs

MIRI imaging will be obtained in all 7 filters using SUB256 with a 5 position cycling dither for Uranus, and 4 filters for using SUB64 with a small Gaussian dither for Neptune (Neptune is 100x brighter than Uranus in most bands).

Per Dirunal Sampling

Total for 4 dirunal samplings and 2 epochs

NIRCam Imaging of Uranus - 38.1 hrs NIRCam imaging will be obtained in 3 filters for isolating methane absorption features to constrain the atmospheric vertical aerosol distribution. A small INTRASCA dither pattern 4 sub- pixel dithers will be used for each observation.

Per Dirunal Sampling

Total for 4 dirunal samplings and 2 epochs

MIRI IFU Uranus - 15.4 hrs The MIRI IFUs range in size from ~3.0" x 3.9" at the shortest wavelengths, to ~6.7" x 7.7" at the longest, and will provide simultaneous spatial and spectral (R ~ 2000 - 3700) data on selected regions of the planetary disk. Due to the wavelength dependence of the IFU fields of view (FOVs) and the similarity of the size of the FOVs and the angular diameter of the ice giants, a four-position dither pattern will ensure adequate spatial and spectral sampling across the planet.
A sky chop will be executed.
Per diurnal sampling
Total for 4 dirunal samplings (with one sky chop) and 2 epochs
NIRSpec IFU Uranus - 28.3 hrs The NIRSpec can perform observations of ice giants using fixed slits. Alternatively, NIRSpec is equipped with a 3" x 3" integral field unit (IFU) that is well matched for Neptune observations, and Uranus. A sky chop will be executed.
Per diurnal sampling
Total for 4 dirunal samplings (plus sky chop) and 2 epochs
NIRCam Imaging for Neptune - 38.1 hrs Per Dirunal Sampling
Total for 4 dirunal samplings and 2 epochs
MIRI IFU Neptune - 10.7 hrs Per Dirunal Sampling
Total for 4 dirunal samplings (plus sky chop) and 2 epochs
NIRSpec IFU Neptune - 24.5 hrs Per diurnal sampling
Total for 4 dirunal samplings (plus sky chop) and 2 epochs

CONSTRAINTS:

Moving targets:

Diurnal observations per mode must be nested within a short period (≤2 days) and phased to yield 4 samplings of the longitudinal structure during a rotation of the planet. The option to try to match phase in other ways is not possible because of the event-driven scheduling.

Epochs should be spaced by ~ 6 earth months.

PARALLEL Observations possible (yes/no/pure parallel)?

These are moving targets, so parallels are not appropriate.

PROGRAM COORDINATOR/DATE: D. C. Hines, K. Uckert, N. Chanover, H. B. Hammel/12 December 2011

For more information about this program refer to the latest version of the SODRM.


TITLE: Giant Planet Satellites

ID: 92060

GOAL:

The diversity (size/composition) of the satellites provides natural field laboratory for studies of materials critical for planet formation. Spectra will be used to study the diverse surface composition.

Sample and sky coverage: For each planet, one to five satellites will be observed for Saturn, Uranus, and Neptune. It is desirable to obtain spectra at different phases in the satellite rotation period. We assume 4 samplings, which gives 2x sampling per "face." We emphasize that the diversity is extreme. Three of the faint moons of Uranus could probably be dropped.

NOMINAL ALLOCATION (hours):

168

TARGET(S):

OBSERVING TEMPLATE:

MIRI LRS Spectroscopy
NIRSpec Fixed-Slit

OBSERVATION DETAILS:

Basis for exposure time estimates (S/N & brightness):

TBD, depends upon the satellites selected. S/N about 10. A S/N of about 100 is needed. For most satellites, the magnitudes were derived from parameters in Allen (2000). For Miranda, Porta, Puck, and Rosalind, the parameters came from Trilling (2000). For many satellites, the K-L and V-N colors were missing. In those cases we assumed K-L = -1.5 and V-N = 6, approximating other outer satellites. Conversions from (I, J, K) to AB magnitudes were from the ABmag calculator on the JWST web site.

MIRI LRS - 26.3 hrs NIRSpec Fixed Slit Spectra - 36.7 hrs

CONSTRAINTS:

Moving targets

PARALLEL Observations possible (yes/no/pure parallel)?

These are moving targets, so parallels are not appropriate.

PROGRAM COORDINATOR/DATE: D. C. Hines, W. M. Kinzel/21 December 2011

For more information about this program refer to the latest version of the SODRM.


TITLE: Kuiper Belt Objects

ID: 92070

GOAL:

Objectves:

  • Determine diameters and albedos for a large sample of transneptunian objects
  • Search for evidence of collisionally-induced changes in albedo.
  • Make near-simultaneous measurements to mitigate rotational
  • Observe a large enough sample to search for differences in different classes of objects.
Technique:
  • Measure both reflected light and thermal emission from TNOs with NIRCam and MIRI.
  • Multiple thermal wavelengths allow for better modeling of non-isotropic emission (beaming parameter), unknown pole position, and unknown therma lineria lightcurve uncertainty.
  • A "typical" trans-Neptunian object (TNO) has Teq ~ 42K (R ~ 40AU, p ~ 0.15, T = T0(1-p)1/4(R0/2R)1/2)
  • Crossover from reflected to thermal emission is at λ ~ 10μm
Most lightcurve periods fall in the range from 3-12 hours
  • Measure both reflected light and thermal emission from TNOs with NIRCam and MIRI.
  • Amplitudes vary from <0.05 mag to >1 mag.
  • Most objects have measurable lightcurve (>0.03 mag) ~15% are > 0.15mag (H>5.5).
  • The fraction is expected to increase at smaller sizes.
  • Need near simultaneous observations.
Secondary science objective: search for water ice absorption.
  • 1.5 μm filter samples water ice feature.
  • 3.5 μm filter samples adsorbed H2O feature.
Observe 100 objects

NOMINALALLOCATION (hours):

168

TARGET(S):

100 KBOs

OBSERVING TEMPLATE:

NIRCam imaging

MIRI imaging

NIRSpec slit spectroscopy

OBSERVATION DETAILS:

NIRCam Imaging - 112.5 hrs

MIRI Imaging - 61.2 hrs

NIRSpec Fixed-Slit Spectroscopy - 100 hrs

CONSTRAINTS:

PARALLEL Observations possible (yes/no/pure parallel)?

In general parallels are not useful since these are moving targets.

PROGRAM COORDINATOR/DATE: D. C. Hines, K. Noll/21 December 2011

For more information about this program refer to the latest version of the SODRM.


TITLE: Main-Belt Asteroids

ID: 92080

GOAL: Asteroids represent some of the oldest bodies in the solar system.

  • Organics, hydrates and water in small, outer Main-Belt Asteroids NIRSpec medium-resolution spectra in the 0.9 - 5 micron region will be used to search for organics, hydrated minerals and water ice for a sample of ~100 small (D < 20km) asteroids in the outer main-belt (3.5 - 4 AU). Features from these materials will occur in the 1.5 - 5 micron region; spectra in the 0.9 - 1.5 micron region will constrain the silicate composition of each body so that a more accurate and complete picture can be drawn of the composition of each body, and of compositional diversity amongst objects in that region. Current dynamical models for the evolution of the solar system indicate that a fraction of the objects in this region may have originated much further from the Sun, so those objects may be revealed as a distinct compositional class by these data.
  • Thermo-physical properties of S- and C-type Main-Belt Asteroids MIRI LRS spectra of 15 main-belt asteroids will provide sensitive determination of the temperature distribution on their surfaces, as well as compositional information through the silicate emission features broadly clustered around 10 microns wavelength. The objects were selected to have similar sizes (as determined by IRAS), and are in two groups: A) high-albedo objects near 2.5 AU (S-type), and B) low-albedo objects near 3.5 AU (C-type). Each target will be observed twice in order to better constrain the thermal inertia of surface materials. For objects with large (>0.25 mag) rotational lightcurves the two observations will be timed to coincide with lightcurve minimum and maximum. For objects with smaller lightcurve amplitudes (0.1 - 0.2 mag), one observation will be timed to view the dawn-side, and a second roughly 6 months later will view the dusk-side, emission.

ACTUAL TIME (hours):

150.5

TARGET(S):

MIRI LRS Targtes

1146_Biarmia
1197_Rhodesia
123_Brunhild
1411_Brauna
1421_Esperanto
1471_Tornio
1605_Milankovitch
288_Glauke
3118_Claytonsmith
340_Eduarda
4169_Celsius
550_Senta
653_Berenike
73_Klytia
766_Moguntia

NIRSpec Sample
1089_Tama
1152_Pawona
1155_Aenna
1170_Siva
1226_Golia
1252_Celestia
1318_Nerina
1378_Leonce
1414_Jerome
1425_Tuorla
1458_Mineura
1501_Baade
1503_Kuopio
1504_Lappeenranta
1537_Transylvania
1545_Thernoe
1549_Mikko
1552_Bessel
1742_Schaifers
1743_Schmidt
1808_Bellerophon
1904_Massevitch
1909_Alekhin
2002_Euler
2038_Bistro
2057_Rosemary
2084_Okayama
2153_Akiyama
2169_Taiwan
2179_Platzeck
2185_Guangdong
2191_Uppsala
2201_Oljato
2304_Slavia
2313_Aruna
2321_Luznice
2465_Wilson
2474_Ruby
2512_Tavastia
2531_Cambridge
2695_Christabel
2715_Mielikki
2724_Orlov
2729_Urumqi
2753_Duncan
2904_Millman
2950_Rousseau
2987_Sarabhai
299_Thora
3013_Dobrovoleva
3017_Petrovic
3052_Herzen
3082_Dzhalil
3115_Baily
3389_Sinzot
3406_Omsk
343_Ostara
3591_Vladimirskij
3684_Berry
3724_Annenskij
3872_Akirafujii
3961_Arthurcox
3983_Sakiko
3999_Aristarchus
4006_Sandler
4009_Drobyshevskij
4049_Noragal'
4061_Martelli
4107_Rufino
4124_Herriot
4141_Nintanlena
4159_Freeman
4194_Sweitzer
4222_Nancita
4250_Perun
4343_Tetsuya
4470_Sergeev-Censkij
4500_Pascal
4505_Okamura
4790_Petrpravec
4812_Hakuhou
4889_Praetorius
496_Gryphia
502_Sigune
5105_Westerhout
5236_Yoko
531_Zerlina
5576_Albanese
594_Mireille
5959_Shaklan
6129_Demokritos
630_Euphemia
7083_Kant
770_Bali
896_Sphinx
955_Alstede

OBSERVING TEMPLATE:

MIRI LRS Spectrocopy
NIRSpec slit spectroscopy

OBSERVATION DETAILS:

We will use MIRI LRS to obtain spectra that will constrain the temperature of the asteroid.

MIRI LRS Spectroscopy - 37.5 hrs

Per Target. This is repeated twice for each object.

NIRSpec Fixed-Slit Spectroscopy - 113.0 hrs

NIRSpec Modes

Fixed slit, 0.4x3.8" probably OK (typically ~0.3 - 10 mJy sources)?

Filter Grating Purpose

F070LP G140M 0.9 - 1.3 um silicate features
F170LP G235M H, K band hydration features
F290LP G396M L, M band hydration, H2O ice features, other volatiles

All the spectra for a target should be acquired back-to-back. Sort of like the old chain constraint for Spitzer.

PARALLEL Observations possible (yes/no/pure parallel)?

In general parallels are not useful since these are moving targets.

PROGRAM COORDINATOR/DATE: D. C. Hines, J. Stansberry/12 December 2011

For more information about this program refer to the latest version of the SODRM.