(Editor’s Note: Due to timeliness concerns for events mentioned, we nudged next week’s astro-event up to today!)
After a long drought, the International Space Station (ISS) returns to the nighttime skies this week. And what a return it is; starting tonight on June 23rd, the ISS enters a phase in which it is illuminated by the Sun throughout the span of its orbit. This unique event continues for four days, and sighting opportunities abound. This is only possible within a few weeks surrounding the solstice season, and does not happen again this year. Generally, the farther north or south in latitude you are, the greater the sighting opportunities; areas such as northern Maine, for example, will see the ISS on every 90 minute pass throughout the night! This also produces a dilemma for residents of the ISS, as overheating is a major concern. To offset or minimize this effect, portions of the ISS can be angled to alternately “shade” sections and automated cooling and radiating devices are installed throughout. Now is a good time to spy this celestial outpost of humanity, as its brightness rivals Venus. Spaceweather.com, Orbitron and the NASA ISS website all provide sighting guides; you can even follow @twisst on twitter for sighting ops or our humble feed @Astroguyz if you live in the US Southeast. Our favorite pick for ISS tracking is Heavens-Above, a tried and time honored favorite… let us know of your ISS sighting success stories!
The Astroword for this week is Inclination. This is one of the essential perimeters that defines an orbit of a celestial body; usually an established and agreed upon 0° degree point is set based on the primary bodies’ rotation (as is the case for objects orbiting the Earth) or orbital plane (for objects orbiting the Sun). That is, the Earth’s orbit as traced out by the ecliptic establishes zero point inclination throughout our solar system. The fact that the illumination angle of the ISS changes is a direct result of its 51.6° degree inclined orbit with respect to the Earth’s rotational equator. This relatively high inclination was chosen to be easily achievable between U.S. and Russian launch sites. In order for the shuttle or any spacecraft to reach the ISS, it must match the same magical orbital inclination of 51.6° degrees.