From the Main Belt to the Kuiper Belt Simulating HARMONI observations in the solar system Fraser Clarke With lots of thanks to Ashley Fisher, Leigh Fletcher, Colin Snodgrass, Dane Tice Outline • Simulation techniques • Simulation examples • Resolved/Binary Asteroids – comparative mineralogy • Giant planet moons – surface composition and evolution • Kuiper Belt objects – ice composition • Current observations • Galilean moons • Neptune Simulation techniques • Solar system observations -> solar reflection spectroscopy • Inputs are; • Two-d image (i.e. from model or from in-situ observations) • Reflection spectrum • Standard solar spectrum • Ephemerides (e.g. http://ssd.jpl.nasa.gov/horizons.cgi ) for magnitudes and diameters at time of observation Two-d input images HST ain’t good enough! • In-situ observations from space craft for giant planets • Galileo • Cassini • Voyager • Model based geometries for asteroids • DAMIT : http://astro.troja.mff.cuni.cz/projects/asteroids3D/web.php • Radar / Light-curve inversion based, with rotation model included! Input Spectra • Disc integrated spectra generally • SMASS catalog for asteroids • Patch together different spectral types manually • Lower resolution IFS data for some objects • Standardised solar spectrum (E490-00) • Δλ ~ 10A (good enough for most solar system observations!) • http://rredc.nrel.gov/solar/spectra/am0/ Simulation techniques • Multiply solar with reflection spectrum • Convolve with filter (typ V band) to calculate object magnitude • Scale to get apparent mag at time of observation • End up with fluxed spectrum in e.g. erg/s/cm2/A for object Simulation techniques • Combine fluxed spectrum with normalised image to make a cube • Account for spatial scale of input image – simulator needs a surface brightness • Generate separate cubes for different spectra and combine after Spatially resolved asteroids • ~200 main belt asteroids large enough to resolve with E-ELT / HARMONI • Spectroscopy allows comparison of composition across the surface • Simulation of 15 Eunomia, which has known composition differences across surface • 10 mas scale 15 Eunomia at 10mas/spaxel • 60s exposures 2.1 microns. October 2028 • 2028 opposition (not ideal, but OK!) • Spatial resolution excellent • Still need to try adding in spatially varying spectrum 0.8um 1.2um 1.6um 2.2um Figure 5 from Reed, Gaffey and Lebofsky, 1996. Slope/2.0-micron differences due to changing Pyroxene/Olivine composition ratios Spatially resolved asteroids • ~200 main belt asteroids large enough to resolve with E-ELT / HARMONI • Spectroscopy allows comparison of composition across the surface • Observation of 4 Vesta with SWIFT + PALM3K on the Palomar 200-inch 4 Vesta resolved with SWIFT+PALM3K Asteroid moons Capture or fragmentation? • Simulation of 121 Hermione in August 2027 • V=11.87 • Dia=0.18” • Known moon • ~5.3 mag fainter • 0.5” away • Example observation with 1x120s exposures • Single channel in the K-band • 10mas scale Asteroid moons Still to do : Extract spectra and see if Capture or fragmentation? we can recover the spectral types! • Simulation of 121 Hermione in August 2027 • V=11.87 • Dia=0.18” • Un-known moon perhaps?? • ~10 mag fainter ΔM=5.3 • 0.3” away • Example observation with 20x120s exposures • Single channel in the K-band ΔM=10 • Healthy pinch-of-salt needed! • Simulator uses a smooth PSF • No speckles included at all! • But also no post-processing Courtesy of Colin Snodgrass Kuiper belt objects • Kuiper belt is at a distance where ices are stable on the surface • Contains large bodies that are bright enough for near-IR spectroscopy Luu & Jewitt 1998 • Spectroscopy has revealed a Licandro et al 2006 variety of surfaces • E-ELT will allow us to work further down the mass distribution than current facilities Courtesy of Colin Snodgrass Haumea • 136108 Haumea (or 2003 EL61) is one of the largest TNOs, but a strange one: • Two satellites • Fast spin • Elongated • (Almost) pure water ice surface Pinilla-Alonso et al 2009 • May be the result of a collision, and discovery of dynamically / compositionally linked objects support this • Most are too faint for spectroscopy on 8m • Limited to follow-up via photometry • Good for global properties • Poor for characterising detailed ice compositions Input spectrum Haumea Observed sky subtracted spectra • 1 hour observation of Haumea V=23 spectrum scaled to V=23-26 magnitude • 20 mas spaxel scale • LTAO PSF V=24 • H+K R~3500 spectrum (blue line) • Rebinned down to R~130 (red line) ~20km size object Comet nucleus size… • Simple 3 spaxel aperture extraction V=25 • Feasible to measure surface compositions down to V~24-25 • Comparable to comet nuclei sizes in the V=26 Kuiper belt (depending on Albedo!) The Gas Giants and their moons • The moons of the gas giants, and Io & Ganymede Uranus/Neptune themselves will make Galileo exquisite targets for E-ELTs • AO-assisted ground-based observations highly complementary to in-situ space- craft measurements • Whole disc in (almost!) one shot HARMONI diff • Easy revisits to monitor evolution limited FoV • ELTs offer spatial resolution in the 10’s of km range ; comparable with all but the closest fly-bys Titan Cassini-VIMS Galileo, 1610 The Gas Giants and their moons • The moons of the gas giants, and Io & Ganymede Uranus/Neptune themselves will make Galileo exquisite targets for E-ELTs • AO-assisted ground-based observations highly complementary to in-situ space- craft measurements • Whole disc in (almost!) one shot • Easy revisits to monitor evolution • ELTs offer spatial resolution in the 10’s of km range ; comparable with all but the closest fly-bys Titan Cassini-VIMS Galileo, 1610 Galilean moons – Io ~10 km / spaxel at 4mas Input Galileo in-orbit image HARMONI simulated (SCAO) at (April 1997) 4mas / spaxel (needs a mosaic!) Caveat – HK AO performance used on a visible light image Galilean moons – Io ~10 km / spaxel at 4mas Input Galileo in-orbit image HARMONI simulated (SCAO) at (April 1997) 4mas / spaxel (needs a mosaic!) Colour image using simulation at 650, 800 and 1000nm Galilean moons – Io ~10 km / spaxel at 4mas SWIFT + PALM3K observed at 16mas / spaxel (2012) HARMONI simulated (SCAO) at Input Galileo in-orbit image 4mas / spaxel (needs a mosaic!) (April 1997) Eruption of Pillan Patera Galilean moons – Io volcano in late 1997… ~10 km / spaxel at 4mas SWIFT + PALM3K observed at 16mas / spaxel (2012) Trust the smudge! Input Galileo in-orbit image (April 1997) Galilean moons with SWIFT 80mas/spaxel Galilean moons with SWIFT 16mas/spaxel Galilean moons with SWIFT 16mas/spaxel Observed Spectra (1990s) Ganymede Europa Callisto • SWIFT spectral range 0.6-1.05 µm relatively flat: – Dominant features of water ice (small kink near 1.04-µm). – O2 features denoted as ‘B’ – Hydrated mineral bands all occur longward of 1 µm. – Possible olivine/pyroxene silicate signatures throughout this range? Courtesy of Leigh Fletcher Courtesy of Dane Tice Gas giants Probing Neptune’s atmosphere • Power of IFU really exploited in objects with sharp wavelength features • e.g. CH4 in Neptune/Uranus Neptune Courtesy of Dane Tice 80mas/pixel 640nm to 1040nm in 10nm steps 80mas/spaxel Courtesy of Dane Tice Probing Neptune’s atmosphere • Different wavelengths probe different depths in atmosphere • Spatially resolved spectra allow us to probe for composition variations as a function of position • e.g. Monitor latitudinal CH4 variation previously seen in Neptune Courtesy of Dane Tice (SC)AO performance with wavelength don’t get excited about the visible! 500nm 800nm 900nm 1200nm 1300nm 1800nm 2000nm 2400nm (SC)AO performance with wavelength don’t get excited about the visible! – no really don’t… 500nm This light goes to the WFS! 800nm 900nm 1200nm 1300nm 1800nm 2000nm 2400nm Solar System Objects with HARMONI • SCAO spec’d to work on objects up to 2.5” (goal 4”) • SCAO will not support non-sidereal tracking • OK if target has V<15, otherwise use LTAO • No SCAO capability below ~0.8 microns (LTAO blue cut-off TBC!) • LTAO sky coverage TBC (depends on performance) • Differential tracking up to 100”/hr for ~15 minutes • Need to plan observation carefully to track guide stars! • “No” anisoplanatism effect with LTAO – always on-axis… • Field of view in diffraction limit is <1” • Need to mosaic even for large moons • Atmospheric dispersion makes this worse • Lowest resolution mode is likely to be R~3500 • Get IzJ or H+K at the same time • Low resolution (R~500) prism capability is unlikely to happen • Will need multiple observations to cover full wavelength range.