Recent Results from NEOWISE
Amy Mainzer
JPL
WISE/NEOWISE
WISE
• 4 imaging channels covering 3 – 25 mm
• 40 cm telescope operating at <17K
• Surveyed entire sky 2x
• Surveyed from Jan 2010 – Feb 2011
• PI: Ned Wright, UCLA
NEOWISE
• WISE not a dedicated asteroid mission
• NEOWISE is Planetary Science-funded enhancement to
the main WISE pipeline
• Two tasks:
– Create archive of individual epoch images +
solar system-friendly query tool
– Discover new asteroids with WISE
– Tracklets delivered to Minor Planet
Center within 10 days
– WISE Moving Object Pipeline (WMOPS)
derived from PS MOPS
Wide Field Infrared Survey Explorer
NEOWISE Team
•
•
•
•
•
•
•
•
•
•
•
•
•
PI: Amy Mainzer
James Bauer: JPL/IPAC
Roc Cutri: IPAC
Tommy Grav: PSI
Robert Jedicke: IfA
Joe Masiero: NPP postdoc  JPL staff scientist
Bob McMillan: LPI
Carrie Nugent: NPP postdoc
Rachel Stevenson: NPP postdoc
Dave Tholen: IfA
Russ Walker: MIRA
Ned Wright: UCLA
Students: ~15 so far, including Emily Kramer (UCF), Carrie Nugent (UCLA), Jessica
Watkins (UCLA)
1 YEAR NEOWISE SURVEY
Sept. 29, 2010
Lost all 12 mm
Sept. 29, 2010
- Feb. 1, 2011
3.4 & 4.6 mm only
•
•
•
•
•
•
>158,000 asteroids detected
>34,000 new discoveries
~750 NEOs detected
135 new discoveries
150 comets detected
21 comets discovered
NEOs – NEOWISE-discovered
NEOs – others’ detected
Comets – others’ detected
Comets – NEOWISE-discovered
All other detected objects
Aug. 5, 2010
Lost 22 mm
NEOWISE Science Data Analysis
• Final release of NEOWISE Post-Cryo survey phase
data 5/22/2013
• Rerunning WMOPS at lower SNR
– Test runs at SNR=3.5 yielded 20% more detections,
each with 2x more detections/object (10 20)
• Stacking on all known cataloged objects
• Creating catalog of physical properties in PDS
Near-Earth Asteroid Numbers &
Sizes
•
Use well-known sensitivity &
uniformity of four band survey
to compute total numbers
from observed sample
•
20,500+/-3000 @ 100m vs.
prior estimates of 36,000 –
100,000
•
>90% of 1 km and larger
NEAs have been discovered:
Spaceguard goal
•
Mainzer et al. 2011 ApJ 743,
156
Shallower
slope: -1.32+/-0.14
break
NEOWISE Detections of Small NEOs
• Smallest NEOs detected by NEOWISE are 8m in diameter
– Detected in band W2 at 3-4 lunar distances from the
spacecraft, so similar objects could be detected if WISE is
restarted
– More in data that haven’t been identified yet
• 12 NEOs detected with diameters <25m so far, 7 in band
W2, so could be detected with reactivated NEOWISE
• 100 additional close-approaching NEOs recovered from
NEOWISE data in addition to ~550 published to date; 66
detected in band W2
– Diameters & albedos computed (Mainzer et al. in prep)
Determining Sizes
• IR radiometry allows determination of size &
albedo, can indicate rapid rotation and/or high
thermal inertia
2010 XA11: 10±2 m, 2010 TN4: 13±3 m,
57±25% albedo
12±6% albedo
2010 GH7: 8±2 m,
11±3% albedo,
rapid rotator
2010 FD6: 8±2 m,
55±15% albedo,
rapid rotator
Asteroid Families
•
Masiero et al. 2013 ApJ 770, 7 “Asteroid Family Identification using the Hierarchical
Clustering Method and WISE/NEOWISE Physical Properties”
•
Use albedo + velocity cuts in HCM method to identify new families/family
members w/ ~120,000 Main Belt Asteroids detected by NEOWISE
•
Link ~38,300 asteroids into 76 families
Restarting NEOWISE
•
•
•
Possible to restart NEOWISE & resume survey using bands W1 and W2 only (3.4 &
4.6 mm)
No consumables now, but limited lifetime due to orbit precession
Orbital plane drift rate depends on solar activity
Restarting NEOWISE
•
With baseline cadence, would discover ~50-60 new NEOs/year, 25% of which are
PHAs (vs. <10% from ground)
•
Expect to detect & obtain diameters/albedos for ~2000 NEOs in total after 3 year
survey
•
3 coorbitals detected by NEOWISE in Post-Cryogenic survey phase, including 2
discoveries: horseshoe + Earth Trojan
•
Possible to discover more coorbitals & set improved limits on population
•
Same data delivery policies as before
How Restarting Would Work
•
•
•
•
Spacecraft currently power-positive but pointing at Earth for half of each orbit
Need to resume zenith pointing & wait for cooldown (3-4 months)
Need ~1-2 months to recalibrate distortion, remap bad pixels, etc.
Possible to alter cadence – might improve NEO detectability
NEOWISE Data Use
• Total citation count using NEOWISE data & discoveries up to ~100 refereed
publications
– Total citation count for WISE ~500 refereed publications
• NEOWISE is a synoptic mid-infrared all-sky survey, so its science spans many areas
of astrophysics & planetary science:
–
–
–
–
–
–
–
–
–
–
Asteroids
Meteoritics
Variable stars
Icy bodies in the outer solar system
Distance ladder determinations for cosmology
Human exploration
Supernovae
Pulars
Exoplanets
Black hole accretion disks