NASA is celebrating the 50th anniversary of America’s presence in space with a commemoration of the launch of Explorer 1. Coming just four months after the U.S.S.R. orbited Sputnik, Explorer 1 was the first satellite to carry scientific research equipment into space. The Van Allen cosmic ray detector was the principal instrument aboard Explorer 1. NASA is commemorating America’s First Spacecraft with a special webpage. NASA’s Jet Propulsion Laboratory designed and built Explorer 1’s payload and amateur radio operators who were associated with JPL at the time were directly involved in efforts to monitor Sputnik’s radio signals. This week the JPL amateur radio club station, W6VIO, will conduct a special on air event to commemorate Explorer.

Late January and early February mark important milestones in spaceflight history. The Apollo 1 fire occured on January 27, 1967; the Challenger disaster on January 28, 1986 and Shuttle Columbia broke up on re-entry on February 1, 2003. Here at StarGeezerAstronomy.com we think it is important to pause and reflect on the sacrifices and scientific contributions of the Apollo 1, Challenger and Columbia crews. We also believe that we should celebrate their contributions and the tremendous legacy of missions like Explorer, Voyager, the Mars Exploration Rovers, Casini-Huygens, Mercury MESSENGER and the tremendous ongoing accomplishments aboard the International Space Station. The Expedition 16 crew aboard ISS completed a 7 hour extra vehicular activity, or spacewalk on January 30, 2008. New European and Japanese laboratory modules are poised and ready for transport to ISS in the coming weeks and months.

What better way to celebrate Explorer’s 50th anniversary, NASA’s legacy in space and the men and women who make such accomplishments look easy than observing an orbital pass of the ISS? As it happens ISS will be visible during evening passes over much of North America and the world in the coming days. I’ve selected the “best” passes for the week at selected cities in the U.S. and around the world. To find upcoming visible passes of the International Space Station for your city click here.

Rocky Visitors Cruise Inner Solar System 

A pair of relatively small, rocky interlopers top the list of items of interest this week. A recently discovered asteroid designated Asteroid 2007 TU24 will sweep by Earth at a mere 334,000 miles (1.4 lunar distance) this week. TU24 will be visible for amateurs with small telescopes but at magnitude 10+ this tiny object will be visible only under dark, clear skies. TU24 was discovered by the Catalina Sky Survey on October 11, 2007 and has an estimated diameter of 800 feet. The asteroid’s nearest approach will be 29 January 08:33 UT (3:33 AM EST).

The approach of this object is the closest currently known approach by a potentially hazardous asteroid of this size or larger until 2027. There is no chance of it hitting or affecting Earth. TU24 will be brightest the night of January 29-30. If you have a small telescope or binoculars and access to a reasonably dark site I urge you to attempt to locate and observe this object. Visit NASA’s Near Earth Objects Program site. For an excellent discussion on the TU24 encounter visit the Astroprofs website 

Above: The low-resolution radar images of asteroid 2007 TU24 were taken over a few hours by the Goldstone Solar System Radar Telescope in California’s Mojave Desert. Image resolution is approximately 20-meters per pixel. Next week, the plan is to have a combination of several telescopes provide higher resolution images. Image credit: NASA/JPL-Caltech

The finder chart to the left is courtesy of amateur astronomer Dr. Dale Ireland from Silverdale, WA. The illustration shows the asteroid’s track on the sky for 3 days near the time of the close Earth approach as seen from the city of Philadelphia. Since the object’s parallax will be a significant fraction of a degree, observers are encouraged to use NASA’s on-line Horizons ephemeris generation service for their specific locations. Click the chart to enlarge.

Generate a personalized ephemeris based on your location with the Horizons Ephemeris service

Mars will have an encounter with asteroid 2007 WD5 on January 30th. Although calculations based on observations made by the Space Research Centre at the Polish Academy of Science indicate that chances of an impact on Mars are nil.

The Moon, Venus and Jupiter share a “morning dance”

Early risers will enjoy the “morning dance” of Venus and Jupiter in pre-dawn twilight the next few days. This week I encourage you to observe the apparent motion of the two planets from one morning to the next. Venus’ motion will be the most obvious as it will appear lower and closer to the horizon and Jupiter each consecutive morning.

Venus is swinging away from us and falling toward the Sun. It will reach superior conjunction on the far side of the Sun in June. The two brightest planets will appear about a half degree apart on the morning of 1 February. This will be the closest conjunction for the two planets between 2004 and 2014. Thats Venus to the upper left of a much more distant Jupiter. I suggest you go out and look to the southeast around 7am local time for your area. The chart at the left was prepared using Stellarium, click on the image to enlarge.

Sunday, 3 February the Moon, Venus and Jupiter form a jagged line. The following morning our “dancers” form a tight triangle. See the NASA daily charts for January 31, February 1, 2, 3, 4

Read NASA’s Venus and Jupiter Converge

This diagram of the inner planets of the solar system, courtesy of NASA, for January 2008 will help you understand the relative positions of the planets.

The NASA/Johns Hopkins Applied Physics Laboratory MESSENGER probe arrived at Mercury for it’s first encounter with the Solar System’s innermost planet on 14 January, 2008. The spacecraft imaged some areas on Mercury for the first time. No, the image at the left isn’t the Moon, it’s Mercury.

This is Messenger’s first encounter with Mercury. The probe will settle into a permanent orbit around the planet in 2011.

For the latest Messenger mission updates visit the NASA Messenger site or Johns-Hopkins APL Messenger site.