North Hawaii News Articles from CFHT

Last Chance to see Iridium Flashes

For the past few years, one of the most dramatic shows in the sky has been a human creation. In recent weeks, the source of this celestial display has been making headlines in the financial news: the Iridium Corporation.

Iridium was an exciting idea which some claimed was the way of the future, and others feared would be a business disaster. Now it seems the pessimists were right. The idea was to provide true global mobile telephone service by creating a network of satellites in low orbits. These satellites would act like cellphone stations and provide service to people with special portable phones, anywhere on the planet. Any single satellite would only be visible for a short time from a specific point on the ground. The satellites would pass calls along to the next visible satellite, just as a cellphone station does when you drive from one zone to the next. To ensure global coverage, Iridium needed a constellation of 66 satellites.

This was clearly a big, bold project, and it needed big, bold amounts of money. One of the primary investors was Motorola. This was the first time that a large number of satellites were mass produced on anything like this scale. In the past, most satellites have been custom designed, each one starting nearly from scratch. The simple fact that Iridium managed to build and launch 66 satellites was a major achievement. They also managed to keep the cost per satellite quite low, compared with the typical high cost of satellite development, construction and launch. Nonetheless, the total cost has been estimated at between 5 and 7 billion dollars.

Iridium successfully launched their constellation of satellites by November 1998, only a bit later than planned. Service started soon after that. Difficulties started to crop up early on: although the cost per satellite was relatively low, it still exceeded the goal. During launch, a few satellites failed and had to be replaced. But these are the sort of setbacks a new company attempting something daring expects to encounter. The real problem was that not enough people were buying their product.

From the beginning, Iridium expected to sell the service to world-traveling business executives. However, in the years between concept and deployment, ground-based mobile phones became widely available in cities throughout the world. Given with the weight of the Iridium phones and the high expense ($3000 to sign on, $7 per minute), Iridium could not compete. This year, on March 18, after months of trying to find additional cash from a new investors, Iridium declared bankruptcy and stopped service. Over the next two years, they plan to send the satellites into the atmosphere, burning them up. The 5 billion dollar investment will literally go up in smoke.

The demise of Iridium will mean the end of the phenomenon of "Iridium flashes". It turns out that the Iridium satellites are unusual in having a very large, very smooth pair of flat metal plates which act as antennae. When one of these antennae is pointed in just the right direction, it reflects the light from the Sun to the Earth's surface. From the ground, you can easily see the flash of light with your eyes. In fact, the flashes can be much brighter than Jupiter and last for 10 or 20 seconds. They can even be seen in the daytime!

Since the satellite orbits are very well known, it is actually quite easy to predict when a flash can be seen from a given spot on the Earth, and several web sites provide this information. One particularly good web site along these lines is www.heavens-above.com. On this web site, you can specify your location, either by giving longitude and latitude, or by selecting your town from a list. Not only is Waimea included, so are Kawaihae and Honokaa! That is quite impressive, considering the web site is based in Germany.

A specific flash can be seen from only a very small area on the ground. At the best location, the flash can be roughly 100 times brighter than Jupiter is currently; moving only 10 miles away, the flash fades to the brightness of Jupiter. The center of the flash generally moves from South to North. I have compiled a list for readers of upcoming flashes in April. The list also notes if the flash is best seen from the west side of the Big Island (centered on Kawaihae), the central areas (centered on Waimea), or the east side (centered on Honoka'a).

To view one of these flashes, it is best to be ready a few minutes ahead of the time given. Face the compass direction listed for the flash (N, SW, etc) and the flash should be visible above the horizon at the angle given. Remember: 90 degrees means straight up, 45 degrees means halfway up.

The Heavens Above web pages, as well as many others, also tell when and where you can spot a large number of other satellites. No other satellites are as bright as the Iridium flashes. Even so, some are bright enough that they are easily visible in the early evening (or early morning for the early risers). These satellites can be seen as bright stars moving slowly across the sky. In particular, with one click you can get a list of all of the times when Mir or the new International Space Station can be seen. These are two of the brightest satellites since they are both so large. So, head outside and try your hand at "artificial astronomy".

Eugene Magnier

Iridium Flashes for April visible from North Hawaii
Date Time best seen from altitude direction
April 02 08:08:54 pm Kawaihae bright 25 deg N
April 03 08:02:39 pm Honoka'a bright 27 deg N
April 09 07:34:46 pm Kawaihae bright 35 deg N
April 10 07:28:31 pm Waimea weak 37 deg N
April 13 08:09:07 pm Waimea bright 47 deg SE
April 14 08:03:08 pm Honoka'a weak 47 deg ESE
April 16 07:00:58 pm Kawaihae medium 42 deg NNW
April 17 06:54:41 pm Waimea bright 44 deg N
April 18 07:47:41 pm Kawaihae medium 57 deg SE
April 19 07:41:27 pm Waimea bright 57 deg SE
April 20 07:35:35 pm Honoka'a medium 56 deg SE
April 25 07:14:09 pm Kawaihae medium 67 deg SE
April 26 07:07:50 pm Waimea medium 67 deg SE