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PICTURE, a sounding rocket to characterize the debris disk of Epsilon Eridani
Ewan. S. Douglas1 ([email protected]), Chris Mendillo2, Brian Hicks2, Jason Martel2, Timothy A. Cook2, Ron Polidan3, Supriya Chakrabarti2.
1
Department of Astronomy, Boston University, Boston, MA. 2Center for Atmospheric Research, Department of Physics, University of Massachusetts Lowell, Lowell, MA. 3Northrop Grumman Corp.
ABSTRACT
Epsilon Eridani Debris Disk:Reidemeister et al.: ε Eridani
et
10
IRAS
MIPS
MIPS (SED)
SHARC II
SCUBA
1.5
1
PICTURE FOV
0.5
-1
0
10
100
wavelength [µm]
1000
10
1533
Science and Wavefront 1024x1024 pixel, back-illuminated
CCDs from Astro-E2 X-ray mission
Sensing CCDs
Inner &!
Outer Working Angles!
1.5λ/d (0.5”) & 5”
Pointing System
Tip-Tilt steering mirror, 5 mas
pointing (Mendillo et al. 2012a)
0
10
grain size [µm]
• Baseline leakage: 1% amplitude (E ) mismatch (limiting central null to 2.5*10
• Measured Flight Deformable Mirror (DM) Surface Figure
• Secondary/Spider Obscuration & Lyot Mask shape
• Template source spectra (e.g. Pickles et al. 1998, via pysynphot) & surface
brightness distribution
• Shot Noise and Dark Current
0
planet 'A'
-1
Purpose!
Rigel
60 Sec
Demonstrate nulling,
record reference PSF
ϵEri, Roll 1
>105 Sec
Characterize Exozodi
ϵEri, Roll 2
>105 Sec
Characterize Exozodi
The first PICTURE launch in and track speckles
(Courtesy
Figure October
13: Left: 2011.
PICTURE
launch. WSMR.)
Right: Telemet
(TM 2) failed
1
10
ediate (10-55A
The most important result returned from the PIC
In flight, the ACS acquired the calibration star, Rigel
drive the star into the acquisition mirror pinhole. The
the live angle tracker GSE display. An additional ACS
the FSM at which point the FPS immediately locked o
200 Hz with a 5 Hz bandwidth. Analysis of the raw ce
that the FPS stabilized the 627 mas RMS ACS radia
also provides a high-precision measurement of the roc
both the ACS body-pointing and the FPS stability
A dustless simulation showing four regionsofof
The predicted 3AU ring can seen above,
scattered light (corners) from the DM at large
The operation of the telescope in flight is confirm
the circle is cut-off by the (horizontally
radii and a residual central leakage from color
the telescope
PSF
wastransmission
much larger than
anticipated,
oriented)
nuller
minima
at
mismatch between Epilson Eridani (210 unknown. Unfortunately, the lightweight primary mi
0” and 0.9”.
second observation) and Rigel (20 second).The remaining hardware was recovered intact and app
not yet been conducted.
U)
Contrast
The 5σ contrast curves at right are derived
from the annular, one pixel wide, standard
deviation of the expected background (from
dustless simulation shown above) versus the
star brightness (as in Bailey et al 2013). The
star brightness is taken to be the peak pixel
intensity of a smoothed, simulated bright
output.
Subtraction of a noisy reference PSF
removes speckles and increases the effective
contrast (solid red line) and enables imaging
the expected inner debris disk.
The Payload
all the disk components is 1.1 × 10−4 .
Model setup
New Primary Mirror
1. Method
seconds after launch, the main science data telemetry
the TM transmitter power during flight. This TM ch
shown in Figure 4, which carries all of the WFS and
data, the in-flight performance of the nuller and activ
of flight data has been recovered, unfortunately this
acquired steering lock and thus the nuller had not be
future analysis for determining some basic functionali
-5)
Backman
et al.
2009 ice mixtures,
Fig. 2. The βadapted
ratio from
of two
silicate
– water
compared to a pure silicate composition, as a function of
size for ε Eri. The bars show the size bins used in the inner
Figure
8. (a) Perpendicular
depth τsimulations
five model
components.
two unresolvedline
inner shows
belts (dashed lines), outer “icy” ring (dotted
(Sect.
4). disk
The
dashedThehorizontal
⊥ vs. position for the
Reidemeister
et al. 2011opticaldisk
line), and ring+halo “silicate” dust populations (dot-dashed line) are shown. (b) Mass surface density vs. radius corresponding to the optical depth profiles in panel
the
dynamical
blowout
= 0.5.
From
the
SED,
Backman
etof
al.β (2009)
Epsilon Eridani’s Spectral energy
distribution
(a), assuming
grain compositions and
material
densities
described
in the limit
text. The
difference
in slopes between the optical depth and mass surface density profiles is
due to radial variation in model particle
properties.
infer
a system of rings, shown above,
(SED) shows
excess at 24um
out a significant flux
AU) ring within 10AU,
r ring (55-a90warm
with a thin ring near 3AU, scattering
and beyond, eindicating
Dustthe
grain
properties
The top panel of Figure 82.3.
displays
model
profile
Figure 9 is a two-dimensional representation of the ϵ Eri
starlight with
anradial
expected
integrated
proposed by Reidemeister et al.
(2011) to be
of perpendicular
optical depth τ⊥ , that is, fractional (unitless)
debris disk system with a linear spatial scale, showing the
-4 F
knee in area
the
IRS
at
∼ 20 µm
in Fig.
brightness
of 2*10
surface
density (m2 of grainThe
cross-sectional
per
m2spectrum
of *.
disk
sub-mm
ring, (inset
halo, and
inner 1)
warm belts. The position of
sustained
byview
solarofwind-driven
Poyntingg. 1. A
schematic
the ε Eridani
system’s
archiof a panel,
classical
feature.warm
Since
exsurface area; e.g., Backman is
2004),
and inphot/sec
the bottom
the silicate
the innermost
belt the
is compared
in the inset figure with
(Freminiscent
for PICTURE).
* ~3e8
Robertson
drag.
Example wavefronts from the DM mirror arm of the nuller.
cture. The
outer ring
is the region where
the dust mass
is procorresponding
surfaceact
density
inferred
from
the
optical
one
orbit
solution
for
the
candidate radial velocity planet
composition of those silicates is not known, we have
ced by parent planetesimals; the intermediate
zone grain
is the
depth and model
properties
is displayed.
The slopessilicate
of the (Laor
(Section
5.4).
chosen
astronomical
& Draine
1993) (ρd =
two functions
across the sub-mm ring−3and halo are not equal
e where it is transported inward by drag
forces, possibly
3.5 g cm ). On the other hand, by analogy with5.the
surDISCUSSION
because
the model
includes smooth variation in the particle size
eracting with a presumed outer planet;
transport
continface composition
ofofKuiper
the solar system
the fiducial
radii, so the ratio
particle belt objects in
5.1. Some Implications of the Disk Model
s through the inner region where dustdistribution
interactsbetween
with the
(e.g.,
Barucci
al. 2008),
cross section (and thus optical
depth)
to massetsurface
densitywe may expect many additional
own inner planet. Two possible orbits varies
of the
innerwith
planet
slightly
radius. The
optical depths
and ices
mass densities
The derived
surface-densityitprofile
species
such as
and organic solids.
In particular,
is for the small grain come shown. The outer part of the sketch (>
10two
AU)
is rings
not to
of the
inner
in Figure
8 are calculated
by assuming
∆r to be
ponent
(Figureespecially
8) has a nearly
natural
to expect
water ice
present,
givenconstant value from 35 to
ale. Inset: The observed SED. The IRS
spectrum
(dots)
values
of 1 AU at
3 AU and 2 AU at 20 AU; they would scale
110 AU,
consistent
with very
dynamics
controlled by P–R radiation
that
the
source
of
dust
is
a
”Kuiper
belt”
located
far
with
drag or its corpuscular wind analog (Section 5.3). In contrast,
ms from dust in the inner region andinversely
exhibits
a ∆r.
charac- from the star (∼ 55–90 AU), and
star itself
has has
a late
Theµm.
total The
inferred
mass in detected grains, that is, with sizes
the the
large-grain
component
surface density rising from 35 to
istic “plateau” (“shoulder”) at λ ≈ 20–30
main
class. Accordingly,
tried
mixfrom a few microns to a fewspectral
hundred microns,
carrying most of we also
90 AU.
Thehomogeneous
larger grains are less
subject to drag forces, so their
rt of the SED with a maximum at λthe≈radiating
70–80 surface
µm, well
area, is tures
roughlyof
5 ×astrosilicate
10−3 M⊕ ∼ 0.4 with
MLuna , 50% radial
and distribution
70% volume
fraction
may reflect
that of the underlying parent-body
obed by several photometry points (symbols
with
90% of which
is inerror
the large of
(“icy”)
grainice
component
of the sub- 1998)
population.
water
(Li & Greenberg
(ρd = 1.2 g cm−3 ). The
rs), derives from the outer and intermediate
mm ring. regions.
The total bolometric
fractional
luminosity
(Ldice-silicate
/L∗ ) of
The void is
interior
to thegsub-mm
bulk
density
of these
mixtures
ρ = 2.35
cm−3 ring is inferred to be partly
in
ter
m
filled by two additional belts of particles with mean sizes
and ρ = 1.89 g cm−3 , respectively. The optical constants of
the mixtures were calculated by effective medium theory
with the Bruggeman mixing rule. In all three cases (pure
astrosilicate, two ice-silicate mixtures) the dust grains were
assumed to be compact spheres.
New Deformable Mirror
new lightweight
Carbide
primary
mirror
is
pressure
Radiation
ur modelAincludes
gravitationalSilicon
forces from
the star
and 2.4.
new MEMS
currently
being
manufactured
by Northrop
Grumman
AOAconstants
Xinetics.and adopting MieAtheory,
inner planet,
radiation
and
stellar wind pressure,
drag Using
the optical
deformable
ces induced by both stellar photons and stellar wind par- the radiation pressure efficiency Q , averaged over
the
rp
les (Burns et al. 1979), as well as collisions. Dust produc- stellar spectrum, was calculated as a function of
mirror
size sfrom Boston n in the outer region and dust transport through the in- (Burns et al. 1979; Gustafson 1994). We then computed the
Micromachines is
mediate region are modeled with a statistical collisional radiation pressure to gravity ratio, β (Fig. 2). The resulting
prepared for
de. To study the dust in the inner region, we need to han- β(s) was utilized to compute the direct radiation being
pressure
e dust interactions with the inner planet. These cannot and Poynting-Robertson forces.
integration.
treated by the collisional code, so we model the inner
The figure at right
gion by collisionless numerical integration.
shows the 2.5. Stellar wind
expected
flattened The
stellar
wind
was
included
by
a
factor
β
/β,
which is
sw
2. Stellar properties
surface figure.
the ratio of stellar wind pressure to radiation pressure:
SiC mirror,
⋆ = 0.83M⊙
e assumed Example
a stellar20”mass
of M
New primary mirror undergoing initial figuring.
βsw
Fsw
Ṁ⋆ vsw c Qsw
enedicthttp://www.northropgrumman.com.
et al. 2006) and a luminosity of L⋆ = 0.32L⊙
=
=
,
(1)
i Folco et al. 2007). For the stellar spectrum we used a
β
Frp
L⋆
Qrp
xtGen model (Hauschildt et al. 1999) with an effective
mperature of 5200 K, log g = 4.5, solar metallicity, and where Qsw is the efficiency factor for stellar wind pressure
70 seconds after launch.
Simulated ϵEri observations
7. FLIGHT, ANOMALY, RE
after subtraction ofPICTURE
dustless
Rigelfrom
PSFWhite Sands Missile Ran
launched
Simulation Inputs:
Inner Warm Ring
10
Observing
Time
Interfering the PICTURE wavefronts:
Outer Warm Ring
)
e r ( <1 0 A U
TARGET
Nuller performance is simulated by interfering the complex wavefronts of the sheared nuller arms
and generating the resultant point-spread-function (PSF) for a list of discrete points, composed of
the central star and the warm inner ring, with POPPY (Physical Optics Propagation with PYthon)
70% ice + 30% astrosil
50% ice + 50% astrosil
[Perrin et al 2012, github.com/mperrin/poppy]. We computed the polychromatic PSFs in parallel
100% astrosil
using PiCloud.com, which after stacking and addition of noise, produce realistic images.
blow-out limit
-2
inn
Visible Nulling Coronagraph,
600-750 nm, shear of 0.15m
Nuller
10
planet 'B'
0.5 m, f/12.3 Gregorian
Telescope
!
0
β-ratio
ou
te
r
excess flux [Jy]
2
an
pl
Observing Plan
Mission Properties
The PICTURE (Planetary Imaging Concept Testbed Using a Rocket Experiment) sounding
No.interferometer
2, 2009
EPSILON the
ERIDANI
DEBRIS DISK
rocket will demonstrate a nulling
(a “nuller”) to characterize
exozodiacal
dust
disk of Epsilon Eridani (K2V, 3.22 pc) in reflected visible light to an inner radius of 1.5 AU (0.5”)
from the surface of the star. The first launch of PICTURE suffered a telemetry failure and the
primary mirror was shattered upon landing. A new launch is scheduled and the PICTURE
payload is currently undergoing refurbishment, including receiving a new SiC primary mirror.
PICTURE visible light observations will constrain scattering properties of the Epsilon Eridani
exozodiacal dust and debris environment. Measuring the dust brightness of the system
constraints the background which must be overcome for future exoplanet observations.
Additionally, PICTURE will demonstrate operation of a MEMS deformable mirror and a visible
nulling coronagraph in space. Improved modeling and post-flight measurement of instrument
performance allow us to present refined exozodiacal dust sensitivities.
Future prospects look towards a PICTURE refligh
and technology goals of the first mission. In addition,
flight. A number of hardware upgrades have been iden
contributors to OPD in the nuller, the telescope pri
rigid SiC primary would narrow the void between labo
performance in both environments with a similar are
available from BMC. A drop-in replacement could be
electronics. The nuller calibration system could also
that does not obscure the calibration reference beam.
avenue for data post-processing.
Acknowledgements:
(Mendillo et al. 2012b)
PICTURE is funded by the National Aeronautics and Space Administration,
Proc. of SPIE V
Grant NNX13AD50G. Boston Micromachines
Corporation provided DM surface
Downloaded From: http://proceedings.spiedigitallibrary.org/ on 12/14/2012 Terms o
measurement data used for this work.
Thanks to D. Hammerle and T. Bruno at AOA Xinetics for their help and
assistance in refurbishing the PICTURE telescope.
References:
Backman, D., M., et al. 2009..ApJ 690,2.
Bailey, V., et al. 2013. ApJ 767, 31.
Mendillo, C. B et al. 2012a. Applied Optics 51, 29.
Mendillo, C. B., et al. 2012b. In Proc. SPIE, 84420E–84420E.
Perrin, et al. 2012. In Proc. SPIE, 8442:84423D–84423D–11.
Pickles, A. J. 1998. PASP, 110, 749.
Reidemeister, et al. 2011. Astronomy & Astrophysics 527, A57.
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