Tag: Earth-orbiting satellites

Iridium Flares and NOSS satellite pairs

With storm systems and cold fronts moving across the region last night the opportunity to do any sky watching seemed remote. And, yet, for a brief period, clear skies revealed the stars, moon, and satellites above northern Arizona.

First up was the X-37B at ~1805 MST. I watched — but did not photograph — this USAF spacecraft. I wish that I had because for a few seconds after it had passed maximum altitude it flared brightly – possibly rivalling Jupiter in brightness.

Iridium 98 satellite flaring along with the NOSS 2-2 (C) and NOSS 2-2 (D) satellite pair.
Iridium 98 satellite flaring along with the NOSS 2-2 (C) and NOSS 2-2 (D) satellite pair.

Next up was an Iridium 98 flare that was forecast to brighten to magnitude -6.5. This was easily captured by the camera but I was also able to capture two additional satellites travelling close together. A bit of investigation revealed that these were likely NOSS 2-2 (C) and NOSS 2-2 (D). NOSS is the Naval Ocean Surveillance System and these spacecraft travel in pairs and triplets.

I often use the information available at the Heavens-Above web site for satellite tracks and times. Below are the tracks for the Iridium98, NOSS 2-2(C), and NOSS 2-2(D) spacecraft.

Track of Iridium 98 for 12 November 2011.
Track of Iridium 98 for 12 November 2011.
Track of NOSS 2-2(C) for 12 November 2011.
Track of NOSS 2-2(C) for 12 November 2011.
Track of NOSS 2-2(D) for 12 November 2011.
Track of NOSS 2-2(D) for 12 November 2011.

There are hundreds of active satellites and thousands of objects (live satellites, dead satellites, and pieces of space debris) orbiting the earth. So it’s pretty easy to look up and see one of these moving across the sky. But it also makes it difficult to photograph the stars, planets, and other celestial bodies without getting a satellite track across the image.

Another Space Station in the Sky

We all know about the International Space Station (ISS). Many people have watched as it flies overhead as a brilliant point of light moving across the sky.

But now it is no longer the only space station in the sky. On 29 September 2011 China launched its own space station known as Tiangong (“Heavenly Palace”). It’s not as bright as the ISS and thus less noticeable to most observers.

Tiangong and Shenzou spacecraft moving across the pre-dawn sky.
Tiangong and Shenzou spacecraft moving across the pre-dawn sky.

Then, on 01 November 2011, China launched the Shenzhou-8, an unmanned spacecraft designed to dock with Tiangong. And early on the morning of 02 November 2011, both spacecraft passed overhead cutting through the constellation Orion. Just a few hours later, Shenzou-8 successfully docked with Tiangong.

The dual spacecraft flyby is reminiscent of the ISS-Shuttle flybys.

A bright flash in the sky

There are hundreds of operational satellites and thousands of unused satellites and satellite fragments orbiting the Earth. A few of these are quite bright and easy to see as they traverse the sky. Most are dim and generally not easily visible. And others are usually dim but briefly flare much brighter.

Satellite flare is caused by the reflective surfaces on satellites reflecting sunlight directly onto the Earth below and appearing as a brief, bright “flare.” The Iridium satellite series is especially conducive to reflecting light back to the earth and these flares can be exceptionally bright.

Satellite flare from Iridium 91 as it traverses the northern Arizona sky.
Satellite flare from Iridium 91 as it traverses the northern Arizona sky.

Here is an example of the Iridium 91 satellite as it traversed the northern Arizona sky and quickly brightened to a magnitude of -7.0 . Only the Moon (-13) and the Sun (-27) have brighter magnitudes.

Detail of a satellite flair from Iridium 91 as it traverses the northern Arizona sky.
Detail of a satellite flair from Iridium 91 as it traverses the northern Arizona sky.

Knowing when and where to look for Iridium flares is easy as there are many web sites that provide this information. My favorites are Heavens-Above.com and CalSky.com. Happy satellite viewing!

Hello, world!

Welcome to Flagstaff Altitudes at dblanchard.net/blog

My interests include photography, mountain biking, skiing, trail running, and weather. So that is what I will talk about.

For starters, here is a recent photograph taken mid-evening. Down low on the right is the planet Venus. High up near the top is Mars (reddish orange) next to the star Regulus (blue-white). The streak in the upper left is the still-classified USAF X-37B space plane. It looks a bit like a smaller version of NASA’s Shuttle.

Venus, Mars, Regulus, and USAF X-37B
Venus, Mars, Regulus, and USAF X-37B

Two of my favorite sites for getting information on satellite transits across the sky are SpaceWeather and Heavens-Above.

David