Notes from Day 1 of 2011 IAA Planetary Defense Conference. Follow twitter feed for more information:
Day 1 (Monday 09 May 2011) Session 2
- Alan W. Harris
"Update of Estimated NEO Population and Current Survey Completion"
working at small company (MoreData!) and consultant to NASA/JPL NEO program office
estimate population by re-detection ratio (how many you find versus that you have already found), bias correction from computer surveys, and extrapolation to smaller size
results are getting boring since numbers not changing too much, estimate of population through July 2010
re-detection ratio from Mag 23 to Mag 16 on chart of size and number (compare fraction of new discoveries versus total), "r" = re-detection ratio will always be a higher number (getting bias correction is needed), re-detection limits are large end since found many of them (not good are factional probability for low probability numbers), for small objects % of re-detection is very low, go to computer sim of a survey, make a sample survey and look at various size ranges and compare with actual re-detection ratio,
LSST gets 1 week warning (2008 TC3 type object), current surveys give 50-50 chance for those things in a few days prior to impact
Q: Bias in MPC, scoring algorithm from MPC - some bias?
A: Surveys have to be tuned to be quick, would not rely on MPC confirmation page to do that if looking for the short term impact, on calculating existing population using MPC data - things off confirmation page but keep information
- Don Yeomans and Alan Chamberlin
"Comparing the Earth Impact Flux From Comets and Near-Earth Asteroids"
NASA JPL
Define Long Period Comets (LPCs) wild cards of impacting population, period > 200 years, not active until inside Jupiter, takes only 9 months from Jupiter to Earth's orbit, could strike at 51 km/s, 3x that of typical NEO, impact energy is about 9 times that of similar NEA, comet densities are 0.6 g/cm^3 (given this, energy of LPC is only 2x of NEAs)
Compact impact flux study in 1984: rate of comet finding during telescope era was constant (even with increasing technology), average interval between collision is ~43 M years
Also looked at direct date from JPL NEO database, close approaches of comets/asteroids = 0.1%
For current surveys NEAS are important, once the next generation survey is complete, then perhaps comets are next
Largest PHA is Toutatis (5km)
- Ed Beshore
Univ. of Arizona
The Catalina Sky Survey, Past, Present, and Future
PI of Catalina Sky Survey
started in 2002 in NEO business, took over as PI for Catalina
started as an undergrad research project with Tim Spahr, Steve Larson, Carl Hergenrother, John Brownlww, used films in 1994 at start, 3 telescopes:
Mt. Bigelow, AZ (0.7 m Schmidt), routinely used for 24 nights around new moon, around 20th magnitude as 1.2 sigma, 2.5 pixels, in the survey business, coverage is everything, telescope has fallen into disuse,
Mt. Lemmon (1.5 m) reflector, around 22th magnitude, fell into disuse, and took over,
Siding Spring, AUS (0.5 m Uppsala Schmidt), around 19.5 magnitude,
Use identical cameras for all telescopes, 14 second downloads, CyroTger cooling, do not use filters
Base survey on pre-defined fields, 4 images 10 minutes apart, one observer will looks at 6k 3observations per night,
Continuous refinement pays off in development
Many false detections are stars in background, limiting mag. is approx. ~19.5.
Faster focusing, auto refocusing, 30 minutes spent calibrating focus using automation
Dedicated Follow up telescope, on some evenings spent a lot of time on follow-up,
Moving to next generation sensors: 10.5x10.5K CCD, increases coverage by 2.4x
Small binocular Telescope (MMT 6x1.8 meter mirrors - available in dry storage)
3 Small binocular telescopes, 23.3 Mag (3 units) could be largest dedicated to NEO search, 26 months total cost of $30M for all three systems
- Richard Wainscoat
Univ. of Hawaii
"The Pan-STARRS search for NEAs: present status and future plans"
1.8 m diameter, gradual improving in efficiency, discovered 80 NEas, long term is to
1.4 B pixels (giga pixel camera), 3 GB per image, one image per 30 seconds, 3 TB per night,
operated by a consortium, many aspects of astronomy, nearly all observations are suitable for NEO detection
Camera has 60 CCDs, 56% is survey of visible sky, 5% spent on NEO sessions dedicated
Stellar Transit Survey starting this month looking at adjacent fields,
Data processing and NEO candidate review, false detections are problem, humans screen
Do not follow up on NEO candidates
Losing quite a few NEOs, latency in image processing contributes
Fast moving objects are being lost
Jan 30 used whole night for NEO search, found 19 NEos and 1 PHA, 3 fast movers were lost
3K-6K asteroids submitting per night to MPC
A NEO discovery anticipated of 40 NEOs per month
Bad weather in Hawaii (La Nina weather patterns) causing issues
Future: reprocessing of old images using new processing to start, detection of fast moving NEOs from aligned trails in pairs of observations
Can produce image of static sky, subtract static sky to achieve 0.4 mag. gain, more fainters NEOS to be detected, Pan-STARRS 2 would have better camera - most of funding is there, PS 4 on Mauna Kea. MK is better sight than Haleakala.
- Jones, R.L.
"NEO Detection with LSST"
Univ. of Washington
Large Synoptic Survey Telescope (LSST) multiple science drivers
big primary mirror (8.4 m telescope), 9.6 deg FOV, 3.2 Gpix camera
located in Chile
Ranked #1 groudn based large project,
Why is LSST good for NEOs? short exposure (15 seconds), rapid cadence (2 sets of 2x15 images per night with colors), smallest object 0.5 AU could detect 10 m object
processing requirements link detections into tracklets, link tracklets into tracks, filter tracks by fitting orbits
PHA completeness: assume H=22 at D=140m
in 10 years, normal cadence, LSST is 80% complete at 140 m
in 12 years, NEO optimized, LSST reached 90% complete at 140 m
For 45 m objects, LSST's warning time would be between 1-3 months
Not a completed telescope, in design and development phase, federal construction funding from NSF/DoE, 2014, first light in late 2017, first engineering light in 2018, full science ops in late 2019, Mountaintop construction started, processing pipelines under construction, federal construction from 2013-2019.
Q: Colors for small objects which are fast rotators may not be able to occur
A: Colors perhaps not from most objects, but perhaps from some objects
Filter strategy for LSST not settled in terms of changing filters between observations, since filters are large
- Daniel Hestroffer
Gaia Astrometry of NEOs
Gaia's basic aim is 3D census of Galaxy, solar system observation
ESA Cornerstone Mission, launch in 2013, 5 year life, scanning low telescope, ES L2 point
scanning - no pointing, sky coverage in 6 months
- Alan Hildebrand
"NEOSSAT"
Univ. of Calagary
Dual-use missions funded by CSA and Dept. of National Defense
US-based team members supported by
Micro satellite Systems Canada, formerly Dynacon (currently in Phase D)
launch late in 2011 although PSLV schedule may put in 2012
based on MOST spacecraft
50/50 in time in terms of sat tracking and NEO
initially less than $10M, about $15M now with launch slips
Search for NEOs and ATENs, IEOs (interior Earth Orbit)
Every 2 days will discover NEO
- Paul Abell
"Space-Based BEO Survey Telescope in Support of Human Exploration"
NASA JSC
Involved in Hayabusa mission recovery
Human to NEOs is one of the policies of the Obama administration
official policy on June 28, 2010 (Civil Space Guideline #1)
first mission by 2025
NEO Survey telescope suggested by human exploration, science, and planetary defense
Space-based survey telescope is relevant to 2011 Strategic Plan
Asset would be crucial to human exploration
Affordable missions, viable and budget constrained
100 MT launch HLL vehicles, dual launch architecture (cryogenic propulsion stage + CTV + Deep Space Vehicle)
re-entry speed <=11.8 km/s
<=180 day round trip (radiation issue)
2025-2030 missions
NEOs should be of reasonable size for meaningful human exploration (>30m), large diameters are preferred
Within the current database only 1 known NEO >30m in size suitable for 2025-2030 timeframe (2000 SG344, speculation that it is a rocky body)
Importance of viewing geometry: asteroids close encounter with Earth (<0.1 AU) enables both ground and human exploration capability (accessible and observable)
Looked at NEOs with Earth like orbits, took 20 NEOs with these characteristics, 18/20 NEOS have low DeltaV with short duration missions, for each NEO two types of architecture (min DeltaV and balanced)
Looking at short mission and low DeltaV only one (1) that is larger than 30 m
Where and When to look (2015-2020)
A platform in space is needed to fins
Space-Based telescope, launch ready in 4-5 years, SEL1, trailing Venus, SEL2
NEOCamJPL selected for Discovery Call
Program timeline, 2015-2017 NEO Space Survey,
2019-2022 (robotic precursors)
2022-2025 (human mission planning)
2025 launch mission
Q: are robotic precursor needed, what is the latest thinking
A: First time we send people we send precursor (coming from human safety/EVA people), in-site mission informs safety and prox ops and planetary defense topics, precursor can stay there as ob post and data relay
Rusty: in the process, look at increased flexibility if there is a precursor, opens up space of targets
A: Think there are targets but need a space-based system to get better idea of environment
