Discovery safely home at KSC. Next: SRTM Winds just a bit too high prevented Discovery from coming down at the Kennedy Space Center on the first opportunity, but the 2nd window was o.k.: At 00:01 UTC today the orbiter was home. Half a year after the multiple near-failures during the last launch (see Update # 142) had brought the shuttle program to an abrupt halt, it's back on track. Already for late January the next flight is planned, the Shuttle Radar Topography Mission or SRTM. The remaining missions of 2000 were all supposed to be dedicated to the ISS, but with the launch of Zvezda delayed until spring the earliest, no detailled manifest is available. Story filed December 27th Third HST Servicing Mission another full success! All tasks have been completed during the three EVAs without major problems - just like during the first two Servicing Missions in 1993 and 1997. And when the HST was released on Dec. 25th to the minute at 23:03 UTC, it was as 'fresh' as not in a several years. All systems that the spacewalking astronauts had installed were already checked during the EVAs, and after more thorough tests the HST should be able to resume its full scientific operations no later than mid-January. Meanwhile Discovery is being prepared for its return: The first landing attempt is now planned for 22:18 UTC at KSC, starting with a deorbit burn at 21:06 UTC. A second landing opportunity is available at KSC at 00:00 UTC with a deorbit burn at 22:49 UTC. The shuttle will try for one of those two opportunities today. If weather precludes a landing at either time, and the forecast remains good for the 28th and 29th, the shuttle crew will be kept in orbit an extra day to try again at KSC.	Hi-res pictures from the mission are collected in the Spaceflight Gallery! Mission Status Center from Spaceflight Now, official Status Reports from various NASA sources, and a Mission Journal from Fla. Today. Astronaut Grunsfeld reports live from orbit on this special site from S&T! Stories from Dec. 28th: Fla. Today, ESA Science News, Space.com, SPIEGEL, CNN. Stories from Dec. 27th: Fla. Today, SpaceViews, CNN, Space.com, SpaceViews (earlier). Stories from Dec. 26th: Fla. Today, Space.com, AP, Space.com (on HST's status), SpaceViews. Stories from Dec. 25th: Fla. Today, CNN, Space.com, AP, Space.com (astronomers ecstatic), SpaceViews. Stories from Dec. 24th: Fla. Today, Space.com, CNN, Space.com (earlier), AP, SpaceViews. Stories from Dec. 23rd: Fla. Today, Space.com, AP, SpaceViews. Stories from Dec. 22nd: Space.com, CNN. The next mission: SRTM - DLR Page, KSC Mission Homepage, German PR Page. Plus a preview and another one.
Proton's Return to Service in February? The Russian State Commission investigating the Oct. 27, 1999 Proton launch failure is making good progress toward the release of its findings and recommended corrective action, expected now in early January. Proton return-to-flight is now projected to be mid-February. A Russian Government mission that may be ready to launch in this timeframe. The ACeS Garuda 1 commercial mission would either precede this mission or follow shortly thereafter on another pad. A launch date for the Zvezda ISS module has still not been set - recent rumors had shifted it to May...	ILS Press Release. SpaceViews coverage.
Terra's main computer shuts down Another problem for the big Earth observing satellite: The main computer has shut down, though the spacecraft continues to orbit safely. A software change will probably be all that's needed to fix the problem. The computer shutdown was detected on Dec. 21st and is believed to involve the South Atlantic anomaly, where Earth's radiation belts are particularly aggressive - thus one could say that Terra has made its first 'discovery'.	An early AP story. Space.com story and a Status Report on what the problem was.
Weak lensing shows: Galactic halos are huge It's based on test data from the Sloan Digital Sky Survey from a time when the telescope wasn't even properly collimated and when only 225 square degrees of the sky had been imaged - but there are is already evidence with "very high statistical significance" that the dark matter halos of galaxies have enormous diameters. The phenomenon noted in the sky survey's images of thousands of galaxies is "weak lensing": Even diluted masses - like the dark matter in a galaxy's halo - deflect the light from more distant sources somewhat. The effect on galaxies is that they get ever so slightly elongated, with the long axis tangentially aligned with respect to the center of mass. But as all galaxies are already elliptical to some degree, one cannot judge in individual cases whether weak lensing is at work: Many galaxy images must be analyzed together to make the effect measurable - and sky surveys are perfect data surces for that, even a 'shallow' survey like SDSS. The first such analysis with data from the SDSS commissioning phase has promptly shown that "the dark halos of typical luminous galaxies extend to very large radii," typically 1 million light years - the halos of the Milky Way and the Andromeda galaxy would just touch. As the full SDSS will have 40 times the sky coverage plus precise redshifts, a much better analysis will be possible in a few years. What the dark matter in the halos actually consists of, though, these observations don't tell... (Fischer & al., Preprint astro-ph/9912119 of Dec. 7, 1999)	The Preprint, highly technical amd with the title "Weak Lensing with SDSS Commissioning Data: The Galaxy-Mass Correlation Fucbtion To 1h^-1 Mpc." SDSS Homepage. New York Times article on the implications.
The first sunrise of the year 2000... It's not a purely academical question as various exotic island states are actually 'fighting' over the privilege of having "the first sunrise of the new millennium." Even though the millennium starts only at Jan. 1st, 2001, as at least all astronomers know, it's fun to figure out when and where in the world the sun first rises on a location where the calendars show "Jan. 1st, 2000" - and there are several answers indeed: Antarctica at 134.8 degrees East, 66.05 degrees South - here the Sun rises at 15:08 UTC. But it will have been below the horizon only for 30 minutes, and who wants to go to the Dibble glacier anyway? Caroline Island aka. 'Millennium Island' / Flint Island / Antipodes Island (the first two belonging to Kiribati, the latter to New Zealand) - sunrise at 15:43, 15:47 and 15:55 UTC, respectively. None of these small isolated islands is regularly inhabited, however. Pitt Island (Chatham Islands, New Zealand) - at 16:00 UTC the first sunrise of Jan. 1st on a permanently inhabited island (where around 60 farmers live, with scores of sheep). All islands mentioned so far (except Antipodes) can only claim to have "Jan. 1st" on their calendars because they are West of the wiggly - and deliberately drawn! - International Date Line. Taveuni (Fiji) and there Mount Uluinggalau in particular - at 17:23 UTC the first sunrise on solid ground and on 180 degrees longitude. Fiji defends its claim for the 'first sunrise' with particular vigor and is especially angry at Kiribati for recently shifting the Date Line by a huge distance to make it one day later even far East of 180 degrees... Katchall Island (Nicobar Islands, India) - here (and all along a big circle from Northeastern Asia to Antarctica) the sun rises at midnight Universal Time Coordinated which since 1884 is the time for "all the world." However since every country was back then also allowed to have it's own official time as well, the question of the 'first sunrise' just can't be answered. Even less clear, by the way, is the answer to the question "where does the clock strike midnight first?" Both the shape of the International Date Line and the choice of which time zone a location is in are decisions by local governments that don't require international aggreements. Just for fun, e.g., the kingdom of Tonga recently introduced Daylight Saving Time, so that it's midnight there even an hour earlier. Now can they really claim that the year 2000 starts right there, at 10:00 UTC on Dec. 31st? Kiribati's official midnight is at the same time, BTW, and the Chathams follow 15 minutes (!) later...	Links regarding the sunrise issue: ROG Fact Sheet and related maps. A related USNO Fact Sheet. Kiribati celebrates its 'win' of the first sunrise... New York Times story with further insights, BBC Online with an advance report from the Andaman/Nicobar Islands. How things went in Kiribati, on the Chathams and around the world. Picture albums from TIME and the NYT plus various NYT articles. Why the millennium starts only one year from now: USNO Fact Sheet and Millennium Pages and a White House statement. Down with the wrong millennium, says the Manifiesto 2000... Few Y2K glitches in the space sector - the most serious incident was a temporary failure of a ground station used to receive data from reconnaissance satellites, while NASA came through without hardly any trouble: Space Daily, CNN, Space.com, SpaceViews. The most precise clock of the world, or rather the most precise frequency standard, has now started to contribute to the stability of the Coordinated Universal Time (UTC). According to the measurements so far, the NIST F-1 cesium fountain would only deviate one second in 20 million years - though the Cosmic Mirror has learned from the scientists who built the system that it can only operate for a few days at a time (the laser cooling of the cesium is very tricky). Details in a NIST Press Release and a NYT story. More on how UTC and other 'times' work can be found on pages from the PTB, the USNO and the ROG and in a review from Space.com. "The Story of Time" is the title of a remarkable exhibition in the Nat'l Maritime Museum in London-Greenwich that still runs to September. On display is about everything imaginable that has something to do with time, from arcane archaeological and ethnographical artefacts to the most elaborate clocks, compiled from major and minor museums around the world: Exhibition Homepage.

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Compiled and written by Daniel Fischer
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