October 11 – Asteroid 252 Clementina

Asteroid 252 Clementina was discovered on October 11th, 1885, by a very occasional visitor to these pages, Henri Joseph Anastase Perrotin.  As usual for the 1880’s, this is a large main belt asteroid, of about 70 km diameter.  But because Clementina is believed to have been so called after Perrotin’s cat, there isn’t much more I can add as background to the name.

Aphelion 3.396 AU
Perihelion 2.915 AU
Orbital period 5.61 years
orbital speed 16.77 km/second
Semi-major axis 3.156 AU
Eccentricity 0.076
Inclination 10.065°
Longitude of ascending node 202.295°

Pioneer 1 was, naturally, the second launch of the Pioneer programme (the first had been called “Thor/Able 1“, a.k.a. Pioneer 0. Pioneer 1 was launched on October 11th, 1958, and was the first launch by the newly created NASA, which had been set up in July of that year to replace the National Advisory Committee for Aeronautics (NACA, which was pronounced N A C A, not Nasser).

The mission was not an unqualified success, but did provide some useful data. The plan was to send Pioneer 1 into a lunar orbit, to study cosmic rays, micrometeorites, and Earth’s magnetic field. But, due to a premature shutdown of the second stage of the launch vehicle, Mission Control had to settle for a short lived, high Earth orbit instead (about 100,000 km). This was high enough to show the existence of the Van Allen belts, and to measure the density of micrometeorites in our vicinity, and oscillations in Earth’s magnetic field.
It turns out that micrometeorites, despite being only 50 microns to 2 mm in diameter, and weighing as little as 0.00000001 grammes, hurtle at speeds in excess of 10 km/second into the path of our planet to the tune of about 30,000 tonnes per year. It is estimated that approximately 10% of this bombardment survives to reach the surface.

Pioneer 1
Pioneer 1

Another Quick Launch: Apollo VII launched today from Cape Kennedy in 1968, carrying Walter Schirra, Donn Eisele and R Walter Cunningham on their 11 day test mission.

1758  –  Birth of Heinrich Wilhelm Matthias Olbers, the German astronomer who discovered the asteroids Pallas and Vesta.  Olbers also has a paradox named after him.  Olbers’ Paradox is an argument against an infinite and static universe.  Basically, if the universe is unchanging, and populated by an infinite number of stars, any line of sight from the Earth must eventually reach the surface of a star, which means the night sky can’t be black.