near-infrared photometry of venus richard w. schmude, jr. gordon state college
TRANSCRIPT
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Near-infrared photometry of Venus
Richard W. Schmude, Jr. Gordon State College
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Overview
• Purpose of work• Introduction• Method and materials• Results• Conclusions
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Purpose of work
• Determine Near-IR photometric model– J filter (wavelength = 1.25 mm)– H filter (wavelength = 1.65 mm)
• Look for changes
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Introduction
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IntroductionModified from Taylor (2014) The Scientific Exploration of Venus
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Introduction: penetration
• J and H filters penetrate deep– Variation in lower clouds– Large scale meteorology– Super volcanoes?
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Solar phase angle
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Magnitude system
• Developed in ancient times
• The higher the magnitude the fainter the object
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Equipment
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Wavelength
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SSP-4 photometer
• Filter wavelengths– J filter: 1.1 to 1.4 micrometers– H filter: 1.5 to 1.8 micrometers
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Method
Measure comparison star↓
Measure Venus↓
Repeat 2 ½ more times
Star Magnitude: energy units
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Voting Question
What is the purpose of this study?a. Record near-infrared images of Venusb. Monitor the near-infrared brightness of
Venusc. Monitor the brightness of Venus in
visible lightd. The purpose was not stated
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Voting Question
What is the main instrument used in this study?a. CCD camerab. Near-infrared camerac. Hubble Space Telescoped. Gordon State College Observatory telescopee. SSP-4 photometer
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Results: H filter brightness
0 80 160 240
-6
-5
-4
Days after Dec. 31.0, 2014
Bri
ghtn
ess
(mag
nit
ud
e)
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Results: J filter brightness
0 80 160 240
-6
-5
-4
Days after Dec. 31.0, 2014
Bri
ghtn
ess
(mag
nit
ud
e)
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Results
• Compute normalized brightness values– Venus-Sun distance = 1 astronomical unit– Venus-Earth distance = 1 astronomical unit
Astronomical unit = mean Earth-Sun distance
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Normalized J(1,alpha) value
• J(1,alpha) = J – 5.0 × LOG(r × D)
where: J = measured J magnituder = Venus-Sun distance in auD = Venus-Earth distance in au
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H filter normalized magnitude
0 0.4 0.8 1.2
-6
-5
-4
-3
f(x) = 0.977331441952578 x² + 0.458496585567976 x − 5.27230468246382R² = 0.991648758578259
Solar phase angle/100 degrees
H(1
,alp
ha)
mag
nit
ud
es
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J filter normalized magnitude
0 0.4 0.8 1.2
-6
-5
-4
-3
f(x) = 0.959919421878157 x² + 0.708036861679951 x − 5.37002894569564R² = 0.990398424449153
Solar phase angle/100 degrees
J(1,
alp
ha)
mag
nit
ud
es
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Voting Question
As time progressed between January and early July, the normalized magnitude of Venus (J or H filter) _____________.
a. droppedb. rosec. remained the same
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Voting Question
As time progressed between January and early July of 2015, the measured brightness of Venus ________________.
a. droppedb. rosec. remained the same
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Voting Question
As the solar phase angle of Venus rises, the normalized magnitude ___________.
a. risesb. fallsc. remains the same
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AlbedosFilter (Wavelength) Venus Mercury
V (0.55 mm) 0.67 0.132 R (0.7 mm) 0.69 ---I (0.9 mm) 0.57 ---J (1.25 mm) 0.60 0.22H (1.65 mm) 0.42 1.00
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Albedos
0 1 20
0.5
1
MercuryVenus
Wavelength (micrometers)
Geo
met
ric
Alb
edo
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Sources of Near IR radiation
• Reflected sunlight
• Thermal emission
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Conclusions
• Preliminary brightness models constructed
• J and H filters do not penetrate to the surface
• Small variations
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Acknowledgements
• R. Schmude would like to thank Gordon State College for a faculty development grant in 2014.
V, R and I albedos of Venus are from Mallama (2006) Icarus 182, p. 10.V albedo of Mercury is from Mallama (2002) Icarus 155, p. 253.