56 hours of video survey data - Cosmos

Lunar Impact workshop ESTEC ESA Center Noordwijk, 2-3 June, 2015
Observation, analysis and results from 56 hours of
video survey data observed by using one telescope
Ait Moulay Larbi mamoun
PhD student
Atlas Golf Marrakech Observatory
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Moroccan Observatories
Oukaimeden Observatory
Discoveries from Oukaimeden MO““
Ne to teles ope “i e O to er, 2011 :
- 4 comets ! : (C/2013 V5 - P/2013 CE31 - C/2012 CH17 - P/2011 W2)
- 3 NEA ! : (420478)2012 EQ1,(421365)2013 TE129 and (421400)2013 VD14
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Lunar Flashes Observation : Instrumental setup
Watec 902H2 Ultimate
C14 or C8 Telescope
0.33x or 0.63x Focal reducer
Optics : - “C teles ope
or .
- 0.33x or 0.63x Focal reducer.
 Effe ti e fo al le gth ≈
-1150 mm.
GPS antenna
USB Videos
Converter
Data Acquisition : - high speed and
sensitivity sensor (ICX429 EXveiw HAD CCD
technology).
Hight speed Camera
Watec 902H
Time
inserter
C14 or C8 Celestron
Telesope
Computer
AME TIM-10
SCT spacer ring
Focal reducer 0.33x or 0.63x
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Detections:
• From February, 2013 to December, 2014 : (56±2) hours of high quality video data.
- VirtualDub Software : PAL interlaced mode (20fps -> i ; ideo .avi at
×576 pixels.
• LunarScan software is used on recorded videos to perform automated detections.
-Search for adjacent pixels that have collected a sudden illumination with values
that exceed the threshold value defined by the user.
-The dark is subtracted before processing.
• We process the analysis to the whole field of the view (without masks), because
the coordinates stamped by the time inserter are configured to be displayed blackly, and..
we do not want to miss any impact
we want some reference stars near the lunar disk.
• False detections: over a thousand detection (more than 90% of them are one frame events
• os i ra a d ele tro i oise .
Different false detections. Each one
appeared in one half-frame (20 ms).
The full frames are presented here
Bright crater
Flash movement,
indicates a satellite detection
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• Feb 6, 2013
Mag (V): 9.4
• Nov 26, 2014
Mag (V) : 7.1
• Four multi-frame sporadic flashes
• Apr 14, 2013
Mag (V): 7.6
• Dec 25, 2014
Mag (V):9.6
unfavourable lunar phase + inadequate orbital
crossing + weather : have prevented us to
observe at the peak of meteor showers
By using one telescope ,we estimate to have
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missed more than 4 short flashes (1 frame)
Multi-frame flash confirmation :
• The light source shines at the same pixels cluster (no motion across the successive frames )
• The surface brightness profile
• Light curves profile (sudden signal increase followed by a sharp decrease)
+
+
• The magnitude VS flash duration shows a consistency on the trend revealed in Bouley et al,2012
First remarks:
• Among the four flashes, three were detected very close to the terminator.
- 2nd flash : 09.10°±0.15 W; 3rd flash : 2.5°±1 W; 4th flash : 17.50°±0.5 E
• For the 1st and the 2nd flashes, the peak of intensity is reached at the 2nd half-frame.
 The expansion phase has lasted more than 20 ms
1st flash : 60 ms
2nd flash : 160 ms
• The 3rd flash was shorter but brighter than the 2nd !
• The 3rd flash has quickly peaked; while the plume of 2nd flash has required twice more time
to finish its expansion phase.
YANAGISAWA AND KISAICHI 2002
2nd
flash
3rd flash
Dur : 160 ms
Mag : 7.6
Dur : 120 ms
Mag : 7.1
 This can be explained by the fact that fastest meteoroids have capacity to produce bright
and short flashes as clarified in the work of Bouley et al.,2012 in the case of the Leonid impacts.
So, It is more likely that the projectile caused the 4th flash is fastest and which of the 3rd is larger.
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Measured parameters : Date and Time
Longitude and Latitude
Of the site observation
Date
• The impact time :
Raw interlaced frame
Time
first
appearance
separate frames
Odd row field
Even row field
20h 00min 45s 422ms (± 0.01s)
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Measured parameters : Flash duration
?
1
2
3
4
5
-> 5 × 40 ms = 200 ms
positive
Raw sub-images
?
?
Deinterlaced
Sub-images
1
Check negative
Raw sub-images
2
3
4
5
-> 7 × 20 ms = 140 ms
6
7
-> 8 × 20 ms = 160 ms
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Measured parameters : the impact site (to be presented later)
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Measured parameters : Magnitude
• Pretreatment of images (Dark, flat)
8-bit frame from Watec;
Pixel value : 0-255
• Aperture photometry
flux= sum of pixels values
• flu = flu + a kgrou d − a kgrou d
i stru e tal ag itude of a flash = − . × log10(flux)
• During every night of observation and from
time to time we record videos of references
stars (with known magnitudes), and we
measure their instrumental magnitude .
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Deduced parameters : Luminous energy of impact
• The energy received at Earth [J/m2] is appro i ated
usi g Pogso ’s for ula :
E lum_rec = Exposure time × F0 × 10-0.4mv
- Exposure time = 0.02 s
- Mv = V magnitude of the flash
- F0 = 1,5 10-8 J/m2 /s, is the flu fro
a zero
ag itude star i the a era’s pass- a d ≈ . µ
• The radiated energy at the moon is then:
E lum_moon = f × π × d2 × E lum_rec
The emission may be considered hemispherical in early stages of the impact and the expansion phase,
but ongoing the expansion it is more isotropic if we take in consideration the elevation of the plume
above the ground : 2 < f < 3
• The impact energy :
Eimpact = ƞ × E lum_moon
ƞ the lu i ous effi ie
the amount of the initial kinetic energy that is
Converted into luminous energy
• Nu eri al si ulatio :
.
< ƞ < .
, Artemieva et al. 2000,2001
• Leonids i pa t O ser atio : ƞ = .
, the a i u alue
k /s ;Bellot Rubio et al. 2000
-3 exp(-9.32/v2); Swift et al. (2011).
• More s ar s o ser atio : ƞ= .
6/2/2015
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Deduced parameters : Diameter of the produced crater
- The diameter of the crater is estimated from the Gault’s scaling law (Melosh, 1989)
valid for craters up to 100 m in diameter:
• Inputs parameters :
- p Projectile density : to be assumed equal to 3.2 g/cm3 (sporadic asteroids)
- t Target density : to be assumed equal to 1.5 g/cm3 .
- g : lunar gravity.
- E : impact energy.
- θ : impact angel.
p
and θ are better known if the detection is associated with a known swarm of meteoroids
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Deduced parameters : The impactor mass
• By considering Sporadic meteoroid speed in range between 6 and 34 Km/s (Ivanov (2001)),
the impactor mass is:
m = 2 × E/V2
The impact velocity is better known if the event is associated with a known swarm of meteoroids
- According to the statistics of a large sporadic meteoroid
orbit database (Steel 1996; Ivanov 2001).
VEarth= 20 km/s at the Earth, V= 16 km/s at the Moon
- According to NASA Meteoroids Model : V= 24 km/s at the Earth
 B o sideri g gra itatio al fo usi g it’s a out K /s at Moo surfa e
Deduced parameters : The impactor size
• The mean size of the impactor is deduced from the following equation :
D3 = (6 / ) × m ×
-1
p
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Deduced parameters : The Impact rate
• At the Moon
- The impact rate at the Moon surface is obtained by considering the total survey time (56 hrs),
and the average surface monitored (4.8 106 km2).
Annual cumulative number of impacts (E) = N(E) × (365,24×24/65) × (37,8/4,8)
N(E) is the number of impacts with energy higher than E.
• At the Earth
-The terrestrial impact flux is obtained by calibrating the lunar rate in terms of Earth collecting
area by considering gravitational focusing (Suggs 2014;Jones 2007)
Annual Earth flux (Eat_Earth) = lunar flux × (Earth surface × fc /Moon surface)
-Where, fc is a correction factor used to consider the effective cross section of impact
introduced by the gravitational focusing, it is defined by :
fc = 1 + 2(GM/R)×v -2 ≈ 1.3
G is the gravitational constant, M and R are Earth mass and radius (at 100km altitude),
v is the speed of the meteoroid (16 km/s).
- The gravitational focusing increase the meteoroid speed and impact energy is also corrected :
Eat_Earth = E × (1 + 2(GM/R)×v -2 )
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Discussion and Results
• Calculated by assuming a meteoroid speed of 16 km/s and luminous efficiency of 1,5 10-3
• The uncertainties mentioned are associated with the uncertainty of the photometric magnitude
only and does not take into account the uncertainty on speed and the luminous efficiency.
F1
F2
F3
F4
Impact luminous Energy (104 J)
8.2
43
35
4.5
Estimated impact Energy (107 J)
5.4
28.7
23.1
3.0
Estimated mass of impactor (kg)
0.4
2.1
1.2
0.15
Estimated crater diameter (m)
2.6
4.4
4.2
1.8
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Relative uncertainties :
• The impact energy (flash 2)
- The uncertainty engendered by the photometric calibration
(references stars, camera pass- a d… :
%
- The uncertainty engendered by the anisotropic factor of emission (2<f<3) : 20%
- The uncertainty engendered by impact duration uncertainty : 10 %
- The uncertainty engendered by the luminous efficiency : 20%
an extremely large variation with velocity in the range of 6 to 15 km/s.
velocity-dependent
luminous efficiency.
Swift et al. (2011).
0.0015 Value used for
sporadic impact
0.002 Ƞ maximum value
(provided to the fastest
Meteoroids leonids
)
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Relative uncertainties :
• The impactor mass (flash2)
At impact velocity between 6 and 18 km/s, meteoroids with masses between 50 and 500 g
can not be monitored by ground based observation, because the impact energy is below
the detection limit defined by the instruments used until now.
The impact-rate from this impactors class is underestimated.
Be careful if you longing for a holiday on the Moon !
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Relative uncertainties :
-The impact crater size (flash 2) :
• Surface gravity : g = 1.6 m/s2
• Projectile density : 3.1 g/cm3
• Target density : 2.2 g/cm3 (Huang and Wieczorek 2012)
• Impact angel : θ = 45°
D = 4.46 m ±
4.57 m
I we consider
4.02 m
D = 4.46 m ±
4.55 m for θ = 90°
2.90 m for θ = 20°
The crater diameter is mainly
affected by uncertainty around
the impact angle
D = 4.46 m ±
5.27 m
3.73 m
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Discussion and Results
• Light curves
 For long duration flashes, the cooling phase is always longer than the expansion phase.
The cooling phase may have a similar extent or less than the expansion phase for short flashes.
Flash 1 : February 6,2013
Flash 4 : December 25,2014
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Discussion and Results
E = 28,7 107 J
m= 2.1 kg
2nd flash
E = 23,1 107 J
m= 1.2 kg
3rd flash
• The 3rd flash was shorter but brighter than the 2nd !
 Since it is the expansion phase that is considered in the
calculation of energy, the 2nd flash was found more
energetic than the 3rd flash, subsequently generated
by a more massive projectile.
E = 28,7 107 J
; m= 2.1 kg
 The projectile of the 4th flash was faster, which increases
the luminous efficiency, and consequently the brightness.
VMag =7.1 ± 0.2
 But it was smaller, and the vapor-plasma
plume generated has required shorter time span
to accomplish its expansion and cooling phases.
It is susceptible that the average velocity of the plasmavapor components is more important as much as
the impact speed is greater.
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Discussion and Results
• lunar impact rate
- Lunar impact rate can be reached by
considering the total survey time and
the average surface monitored.
Bolides explosions rate in Earth is converted
to the lunar rate.
 Our data (+) are more consistent with
small fireballs flux (---) (Halliday et al.,1996).
A little compatible with extrapolation of :
large bolides flux (---) (Brown et al.,2002).
And lunar impact data given by
Apollo seismic station( ) (Oberst 1989).
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Discussion and Results
• Earth impact rate
Calibrating the lunar rate in terms of Earth collecting area and correcting the impact energy
by considering gravitational focusing.
 Compared to other lunar flashes fluxes,
our data are consistent with flux derived
from [ Suggs et al.,2014] at low energy.
But higher with a factor of 3
in the energy range 108 -109J.
With the same differences, our data are
low in comparison with the rate obtained
by [ Ortiz et al.,2006;
and Madiedo et al.,2014],
Note that :
and
rate supports the
annual flux indicated by large impact
events such as Tunguska and Chelyabinsk.
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Infrared observation :
Setup :
• C14 (20cm) SCT telescope + 0.33x + Camera IR.
• High-speed USB2.0 InGaAs Camera.
• Spectral response 0.9-1.7 µm. (atmospheric transmission window).
• 320×256 pixels array .
Video frames are too small to be supported with lunarScan, due to the small sensor used.
We have
missed the 3rd flash in the IR band :
IR band
- Low spatial resolution ?
-The configuration used in the camera ?
Integration time ; Gain;..
- Inadequate spectral range !
-Light diffusion from the illuminated fraction?
- Optics used (large telescope is required) ?
we tried to use the T600 of Marrakech;
but we were outside of focus. (f /D =3.3 )
Look forward to a future detection, and
hoping that we can exchange the present
camera with the 640 x 512 pixels version.
For high spatial resolution and more light
collection
IR band
IR band
640 x 512 pixels InGaAs array with a 0.9-1.7 µm
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Summary
• The success of the first detections and primarily results has been well proven.
• The first attempts were satisfactory, it allowed us to make confidence on our current
progress in observational and analysis techniques, and to check whether our detection rate is
consistent or not with other impact rates.
• Given the time-consuming workload required to registering and analyzing the videos data,
which is the main limitation to our capabilities, we wish to automate our instrumental setup
in order to increase our detections and be in rendezvous with future lunar exploration.
6/2/2015
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6/2/2015
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