Explorer 1 (APOD 01 Feb 2008)

[Marie Nickell]

In the description for the APOD of February 1, 2008, the writer states:

"Explorer I ... carried ... an experiment designed by James A. Van Allen to measure the density of electrons and ions in space. The measurements made by Van Allen's experiment led to an unexpected and startling discovery -- an earth-encircling belt of high energy electrons and ions trapped in the magnetosphere now known as the Van Allen Radiation Belt ."

This is the accepted history in scientific literature. However, the biographical memoir for Professor John R Winckler, recorded at the National Academy of Sciences website (http://www.nap.edu/readingroom/books/bi ... ckler.html) indicates that Winckler's discovery predates that of Van Allen. Professor Kinsey Anderson writes under the section titled "THE INTERNATIONAL GEOPHYSICAL YEAR, 1957-1958":

"Winckler thought it appropriate to launch a balloon carrying the Minnesota standard IGY payload on the very first day of the IGY. The instrument package left Winckler's hands at 0107 GMT. The balloon reached its maximum altitude and floated there collecting data for 20 hours. During the night a brilliant auroral display appeared over Minneapolis. The Geiger counter and the ionization chamber registered large and rapidly fluctuating fluxes of X rays. Winckler and colleagues interpreted the X rays as bremsstrahlung produced by electrons with energies ranging from 10 to 100 kiloelectron-volt incident on the atmosphere above the balloon. This result was unexpected, although in 1955 James Van Allen's rockoon group had detected "soft" electrons, but the energy of those electrons was not sufficiently high to produce X rays having tens to hundreds of kV energy observed over Minneapolis on July 1, 1957. Van Allen's discovery of geomagnetically trapped energetic particles was still several months in the future and Gold's general concept of the magnetosphere arrived in 1959. In retrospect Winckler's balloon observations can be seen as one of the earliest observed manifestations of Earth's magnetospheric energetic particle dynamics."

Respectfully submitted,
MN

[orin stepanek]

http://apod.nasa.gov/apod/ap080201.html
An interesting observation Marie. How was it found that the radiation was in a belt around the poles?
Orin

[zbvhs]

The fourth-stage booster is still in orbit, I'm told. Might it be possible for the Space Shuttle to swing by and recover it - after the Hubble resupply mission, say? It might be interesting to see what something looks like after 50 years' exposure to the space environment.

[iamlucky13]

No, the empty booster was attached to the instrument section (a separation mechanism would have added extra weight/complexity). It re-entered in 1970. Even so, it was in a fairly elliptical orbit at the time of launch, ranging from 220 to 1500 miles in altitude. The shuttle might be able to match that on a dedicated mission, I don't know, but it doesn't have the fuel to adjust it's orbit from the circular ISS orbit at 183 miles to this looping ellipse.

Also, the Hubble crosses the equator at about a 28 degree angle (inclination). The ISS does so at about a 51 degree angle. Explorer 1 was at a 33 degree angle. All of the remaining shuttle missions will be to one of those two destinations. The shuttle would have to not only match the altitude, but also the direction of orbit. If you don't get both those right, they can smack into each other at thousands of miles per hour velocity difference.

But, if the booster were still up there to be retrieved, it would probably show some pock-marking from micrometeoroid impacts, and maybe some fading of the paint, but that's about it. There would be no corrosion and nothing falling off.