A Blessing or a Curse?

Imelda Joson and Edwin Aguirre timed this 30-second exposure to capture Iridium satellite number 52 as it generated a magnitude –8 flare — about as bright as they get — as seen from a suburb northwest of Boston. Their January 14, 2003, photo on Kodak Royal Gold 400 film was taken with a 70-mm lens at f/4.

Imelda B. Joson / Edwin L. Aguirre

Once smitten by the Iridium bug, you may want to capture flares on film, video, or with a digital camera. Astrophotographer and Sky & Telescope editor Dennis di Cicco's advice is given here. You can get more advice from (and share your results with!) the Internet-based SeeSat-L discussion group, which meets in cyberspace here.

Whether the Iridium flares are a blessing or a curse is a matter of perspective. Apart from their beauty and drama, their predictability makes them a great teaching tool for astronomers seeking to draw the eyes of the public skyward. But along with myriad other communications satellites (to say nothing of the International Space Station), some stargazers deem Iridium flares roving light-pollution sources that contaminate sky photographs and destroy what should be a purely natural experience of the night sky. Radio astronomers have found their observations of interstellar hydroxyl (OH) compromised (and sometimes wholly precluded) by interference from the Iridium spacecraft, which transmit at frequencies that are very close to a critical band reserved by international law for scientific use.

Admired or despised, the Iridium fleet may not be around forever. In order to minimize their contribution to the ever-growing population of "space junk" in low-Earth orbit, the systems’s owners are expected by the U.S. government to bring down any spacecraft that no longer function as part of the Iridium communications network.

In February 2009, the satellite Iridium 33 collided with a defunct Russian satellite over Siberia, and thousands of pieces of debris from that smashup will linger in orbit for many years to go.