IGY Bulletin, Number 6, December 1957 - Whistlers and related phenomena

According to the start of this article in the IGY Bulletin, "whistlers are naturally occurring audio frequency radio waves which, received on an antenna, amplified, and fed to a transducer for conversion into sound, can be heard as long descending whistles."

What do these sound like? Check out this YouTube video of a recording by amateur Mark Dennison in 2010:

This image of the spectrum of a whistler

shows the descending frequency (High pitch to low) of a 3-second whistler signal from over 2.5 kilohertz to about 500 hertz. This falls within the audio spectrum of human hearing from 20 hertz to 20 kilohertz. (Other animals can hear much higher frequencies than humans). 

A figure in the article shows a frequency-vs.-time graph for a whistler that looks the same as the above.

Figure 3 from the Bulletin article, for a whistler bouncing between Alaska and New Zealand. Dispersion D increases with time.

I had my first audiogram two years ago, and although I have the typical moderate falloff for older folks at higher frequencies, I fit into the range above:

My left ear

The Bulletin article points out that the significance of whistlers is that they can provide information about the very high atmosphere, above the altitudes accessible by rocket soundings.

As mentioned in an earlier post, whistlers are generated by the propagation of sferics which then exhibit the property of dispersion whereby signal velocity depends on the frequency. Sferics are transient radio waves arising from naturally occurring electric discharges in the atmosphere. The most intense sferics are produced by lightning.

The figure below from the article indicates how whistler will penetrate the ionosphere, then bounce back and forth between places like Annapolis and Cape Horn that are at the same geomagnetic latitudes in the northern and southern hemispheres, following flux lines (like the dashed one) of the geomagnetic dipole field. Data collected earlier in the year verified such whistler paths that had previously been theoretically calculated.

The article further lists stations set up for whistle observations for the US-IGY program, and gives some of the preliminary findings as of this December article.

I guess if you were an ionospheric scientist working on whistlers, this would be your theme song:

Interesting to read about Adriana Caselotti, the uncredited voice of Snow White.

IGY Bulletin, Number 6, December 1957 - Moonwatch observing methods

This short article in issue #6 of the IGY Bulletin (December, 1957) is an extension of the previous piece.

Moonwatch stations for visual observations of satellites were coordinated by the Smithsonian Astrophysical Observatory, organized by noted astronomer Fred Whipple despite some opposition from professional astronomers. The basic principle was to create a "meridional fence" and observe when that fence was crossed by a satellite. 

In what the article calls the "fundamental method" of observing, a team of observers would train their telescopes on the local meridian (longitude) as indicated by a north-south line and a vertical mast, such that the observing period spanned intervals of time and elevations where the satellite was expected. Then they could note the exact time (right ascension, in one celestial frame of reference) and elevation angle (aka the declination, but not to be confused with geomagnetic declination) where the satellite was seen. As indicated in the figure to the right from the article, the observers had overlapping fields of view so as not to miss the satellite. This must be what the "telescope array" photo that I included in the last post must be showing. Here is a frontal view of an observing team:

Volunteer satellite trackers in Pretoria, South Africa using the fence method, 1965 (Koch)

In the "differential method" of observing, the position of the satellite is measured relative to the known position of a star in the same field of view.

Btw, I find it strange that meridional with an "o" is the adjective form of meridian with an "a."

According to Jenny Koch,

the Moonwatch program lasted for 18 years, with its dedicated volunteers supporting over 400,000 valuable, time-consuming observations of satellites. Long after the buzz around Sputnik ended, Moonwatch remained relevant in providing a low-cost method of collecting satellite orbital data as well as data on the physics of the upper atmosphere. 

 Whipple the President’s Award for Distinguished Public Service from JFK in 1963, the highest civilian honor given to a government employee.

This seems to be a rather extensive guide for the amateur satellite spotter. It opens with the text:

If you have ever star-gazed shortly after sunset or before sunrise, you have probably noticed one or two "stars" sailing gracefully across the sky. These are Earth-orbiting satellites, visible due to the reflection of the Sun's light off their surfaces toward the observer. Hundreds of satellites are visible to the unaided eye; thousands are visible using binoculars and telescopes. Observing satellites has many enthusiasts around the world.

IGY Bulletin, Number 6, December 1957 - Volunteer participation in the IGY Earth Satellite Program

We move on to issue #6 of the IGY Bulletin, from December, 1957. A pdf of this issue (following the Nov. issue), downloaded from the Transactions of the American Geophysical Union, can be found here. This 16-page issue consists of the following articles:

1. Volunteer participation in the IGY Earth Satellite Program
2. Moonwatch observing methods
3. Whistlers and related phenomena
4. Arctic Ocean submarine ridges
5. Oceanographic island observatory in Iceland
6. Second Soviet satellite

In this post, I will review the first article, Volunteer participation in the IGY Earth Satellite Program

The launching of Sputnik on October 4, 1957, highlighted the value of volunteer efforts across the world for satellite tracking. The programs below were to be used for observing both U.S. and Soviet satellites.

The article lists four ways in which volunteers could contribute to the IGY Earth Satellite Program:

a) forming visual observation teams using simple optical instruments. These teams were organized by a special program of the Smithsonian Astrophysical Observatory, named Moonwatch (a former colleague of mine from the F&M astronomy program has a comment after the linked article). At the time of this Bulletin, over 100 such teams had been organized across the U.S., and 62 outside the U.S. It was reported that the Soviet Union had itself organized 66 such stations.

A simple (!) Moonwatch telescope used a mirror to reflect skylight upward into the objective, an arrangement that observing the sky comfortably for hours at a time. 

Moonwatch "telescope array" (Air Force Historical Research Agency)

b) establishing radio tracking stations in coordination with amateur radio clubs, universities, or other scientific groups. This effort was organized under a program called Moonbeam, a secondary network of less elaborate stations run by volunteers to complement the primary Minitrack stations mentioned in an earlier post. Moonbean enabled amateur radio operators to build a simplified version of the Naval Research Laboratory tracking stations for about $5,000 using a “Mark II” system (NASA).

c) recording telemetry signals of scientific data transmitted from satellites by radio and forwarding them to IGY centers. This was done by the same instruments that were used to do radio tracking of the satellites (b).

d) photographing satellite passages across the background star field by means of high quality cameras. A program for this has not yet been formed at the time of the article, but preliminary efforts of te Society of Photographic Scientists and Engineers (renamed in 1992 as the Society for Imaging Science and Technology) had been endorsed.

These efforts would today be termed examples of citizen science. The National Park Service describes citizen science as “when the public voluntarily helps conduct scientific research. Citizen scientists may design experiments, collect data, analyze results, and solve problems. In national parks, most citizen scientists collect data with tools provided by project directors. These data help professional scientists and resource managers answer scientific questions and solve important problems. And the activity helps participants build meaningful connections to science."

The North Museum of Nature and Science, across the street from my house in Lancaster, Pennsylvania, provides opportunities to participate in a citizen science project on plant phenology.

I used the collecting website colnect to search for stamps with the phrase "citizen science." It brought up a set of four Australian stamps commemorating citizen science that were issued last year. I don't own these stamps, but I include depictions and descriptions of them below.