March 2002 Sky from Keeble Observatory

The Hubble Space Telescope (HST), launched into Earth orbit in April 1990, has revolutionized both our view of the Universe and the public's perception of astronomy. Unlike ground-based observatories, HST is not hindered by clouds, weather, or any form of atmospheric disturbance. You may recall, however, that when first deployed, it became the butt of late night talk show jokes because of the flawed main mirror. The 1993 servicing mission installed corrective optics - and the jokes have long since stopped. Subsequent astronauts' visits in 1997 and 1999 have replaced solar panels, upgraded instrumentation, and replaced both computers and gyroscopes.

HST will receive another visit, launched on March 1st after a 24 hour "cold weather" delay, and yet another set of equipment upgrades to help it reach its designed lifetime of 20 years. One more servicing mission is scheduled for 2004. Previous missions to swap out parts have gone smoothly, but NASA cautions that these are challenging tasks - indeed, the complexity of this service call makes it one of the most difficult yet attempted. Solar panels, replaced once, will be replaced yet again. The new panels are smaller, but with improved technology will provide 20% more power. They are rigid and segmented rather than flexible, which should minimize unwanted vibrations as the telescope orbits from sunlight to shadow and back. Their smaller size should reduce atmospheric drag, extending the orbital lifetime.

The primary observing instrument, the Wide Field and Planetary Camera 2 (WFPC 2) was installed on the first servicing mission. Its observing duties will be replaced with a new unit called the Advanced Camera for Surveys (ACS), which has twice the field of view and greater sensitivity. This unit will go into the bay occupied by one of Hubble's original instruments, the Faint Object Camera. The chief HST project scientist, Dr. David Leckrone of NASA's Goddard Space Flight Center anticipates "10 times the discovery potential" as with WFPC. "We can't begin to imagine what we will find." WFPC 2 will remain on HST as a backup to the new camera until its replacement in 2004.

The astronauts on Columbia's mission will also install an experimental cooling system in an attempt to restore operation to the HST's Near Infrared Camera and Multi-object Spectrometer. This instrument has been off-line since a coolant leak in 1999 allowed its temperature to rise above the point where it can usefully observe. The most daunting task is the replacement of the power control system. For the first time since launch, the entire telescope will be turned off. The power control unit was never intended for replacement, so there is some small uncertainty that the telescope can be successfully turned on again. We'll know by next month!

Lunar phases for March: Last Quarter, 8:24 pm on the 5th; New Moon, 9:02 pm on the 13th; First Quarter at 9:28 pm on the 21st; Full Moon on the 28th at 1:25 pm (Passover begins at sunset.)

Evening planet watchers will still have lots to see. Venus appears higher in the western twilight as the month progresses, setting about an hour after the Sun early in the month, stretching to an hour and a half by month's end. Jupiter and Saturn are high to the southeast and south-southwest at the beginning of the month, drifting further west and setting earlier as the month advances. Mars appears about half-way between Venus and Saturn - fading but still brighter than most of the stars in that direction.

An overhead view of the sky at mid-month, finds Castor and Pollux - the twins in Gemini - almost directly at zenith at about 8:30. They mark the eastern edge of the Milky Way, which is seen as a luminous ribbon arching roughly from the southern horizon to the northwest. Below and to the west you will find Aldebaran, marking the eye of the bull in Taurus, and the western edge of the galaxy's glow. Don't confuse it with Saturn, which is close by, but more golden in color in contrast with Aldebaran's reddish hue. Towards the southwest, still dominating the sky, is Orion. Bright red Betelgeuse marks the upper left "shoulder" of the hunter, while the brilliant blue of Rigel marks his knee. Best knows is the belt region, with tempting telescope viewing of the Horsehead nebula, and the Orion Nebula forming the sword. Faithful Sirius, the "dog star" of Canis Major follows to the south. High to the northeast, we find Ursa Major, the Great Bear (also known as the Big Dipper) with its inverted bowl pointing towards Polaris, the pole star. High to the east, Leo is marked by Regulus, the heart of the lion.