1. A Radar Study of Mercury

2. Some Facts About Mercury  Orbital period: 88 Earth Days  Distance from Sun: 0.38 AU (58,000,000 km)  Only 45% of its surface has ever been mapped (by Mariner 10 in 1974-5)  Now Messenger is on its way (will arrive in 2011)  Other studies done with radar imaging from Earth

3. Mercury’s History  Named Hermes by the Greeks, the Romans changed the name to Mercury  Schiaparelli studied Mercury from 1882-9 and stated that its day was the same length as its year! (88 Earth days) This was confirmed by 20 th century observationsThis was confirmed by 20 th century observations  But this is WRONG!

4. Mercury’s History, Ctd.  Pettengill and Dyce (1965) used the Arecibo radio telescope to study Mercury using radar  Mercury rotates once every 59 days! (Not once every 88)

5. Using the Doppler Effect  You can use the doppler effect to measure the rotation of a planet  The side moving away from you is shifted red  The side moving towards you is shifted blue

6. Some Preliminary Calculations  Radar waves don’t come back exactly from the limb  d = ½ c t c = 3 x 10 8 m/sc = 3 x 10 8 m/s  x = R – d  y = (R 2 – x 2 ) 1/2 R = 2.42 x 10 6 m is the radius of MercuryR = 2.42 x 10 6 m is the radius of Mercury

7. Data: What It Looks Like  You will get a “two- shouldered” profile when your signal returns  Measure the frequencies of the left and right shoulders  Be sure to note the T- value (that’s t in your calculations)  Remember that t is in microseconds (10 -6 s)

8. The Velocity of Mercury’s Limb f c = f total /2  f total = the difference in frequency between the two “shoulders” (right – left) V A = (cf c )/2f f is the original radar frequency = 430 x 10 6 Hzf is the original radar frequency = 430 x 10 6 Hz This is all so we can calculate the correct velocity of the planet’s limb:This is all so we can calculate the correct velocity of the planet’s limb: V = V A (R/y)

9. The Rotational Period of Mercury  P rot = C/V C = circumference of Mercury (C = 2R)C = circumference of Mercury (C = 2R)  P rot will be in seconds – divide by 86,400 s/day to get it in days

10. Basic Lab Procedure  Open the Clea MERCURY lab on the computer  Choose the coordinates for Mercury for today (I can show you how)  Send your pulse and wait for it to return  For each echo, note the time and measure the left and right shoulders