New Horizons

New Horizons is a robotic spacecraft mission conducted by NASA. It is expected to be the first spacecraft to fly by and study the dwarf planet Pluto and its moons, Charon, Nix and Hydra. NASA may also approve flybys of one or more other Kuiper Belt Objects. The craft was built primarily by Southwest Research Institute (SwRI) and the Johns Hopkins Applied Physics Laboratory (APL). The mission's principal investigator is Dr. S. Alan Stern of the Southwest Research Institute. New Horizons was successfully launched on January 19, 2006. After a flyby of Jupiter on February 28th, 2007 at 5:43:40 UTC, New Horizons is expected to arrive at Pluto in July 2015 before leaving the Solar System.

The New Horizons spacecraft was launched directly into an Earth- and solar-escape trajectory. It had an Earth-relative velocity of about 16.21 km/s (36,260.7373 mph) just after its last engine shut down, making it the fastest spacecraft launch ever.

New Horizons is the first mission in NASA's New Frontiers mission category, larger and more expensive than Discovery missions but smaller than "flagship" programs.

Key mission dates

• June 8, 2001 — New Horizons picked by NASA over a competing design, POSSE (Pluto and Outer Solar System Explorer)
• June 13, 2005 — Spacecraft departed APL for final testing at Goddard Space Flight Center (GSFC)
• September 24, 2005 — Spacecraft shipped to Cape Canaveral, through Andrews Air Force Base, aboard a C-17 Globemaster III cargo aircraft
• December 17, 2005 — Transported from Hazardous Servicing Facility to Vertical Integration Facility at Launch Complex 41
• January 11, 2006 — Primary launch window opened. Launch delayed for further testing.
• January 16, 2006 — Atlas V rocket launcher, serial number AV-010, rolled out onto pad
• January 17, 2006 — First day launch attempts scrubbed because of unacceptable weather conditions (high winds).
• January 18, 2006 — Second launch attempt scrubbed because of morning power outage at the Applied Physics Laboratory.
• January 19, 2006 — Successful launch at 14:00 EST (19:00 UTC) after brief delay due to cloud cover.
• April 7, 2006 — the probe passed Mars' orbit.
• Early May, 2006 — the probe entered the asteroid belt.
• June 13, 2006 — the probe passed closest to an asteroid 2002 JF₅₆ in the Belt at about 101,867 km at 04:05 UTC. Pictures were taken.
• Late October, 2006 — the probe left the asteroid belt.
• November 28, 2006 — first faint image of Pluto taken from a distance released.
• January 8, 2007 - start of Jupiter encounter.
• January 10, 2007 - Long distance observations of outer moon Callirrhoe as a navigation exercise.
• February 28, 2007 — Jupiter flyby. Closest approach occurred at 05:43:40 UTC at 2.305 million km, 21.219 km/s.
• March 5, 2007 - End of Jupiter encounter phase.
• June 9, 2008 — The probe will pass Saturn's orbit.
• March 5, 2011 — The probe will pass Uranus' orbit.
• August 1, 2014 — The probe will pass Neptune's orbit.
• July 14, 2015 — Flyby of Pluto around 11:59 UTC at 11096 km, 13.780 km/s
• July 14, 2015 — Flyby of Charon around 12:13 UTC at 26927 km, 13.875 km/s
• 2016-2020 — possible flyby of one or more Kuiper Belt objects (KBOs).

Search engine

A search engine is an information retrieval system designed to help find information stored on a computer, such as on the World Wide Web, inside a corporate or proprietary network, or in a pc. The search engine allows one to ask for content meeting specific criteria (typically those containing a given word) and retrieves a list of items that match those criteria. This list is often sorted with respect to some measure of relevance of the results. Search engines use regularly updated indexes to operate quickly and efficiently.

Google

Around 2001, the Google search engine rose to prominence. Its success was based in part on the concept of link popularity and PageRank. The number of other websites and webpages that link to a given page is taken into consideration with PageRank, on the premise that good or desirable pages are linked to more than others. The PageRank of linking pages and the number of links on these pages contribute to the PageRank of the linked page. This makes it possible for Google to order its results by how many websites link to each found page. Google's minimalist user interface is very popular with users, and has since spawned a number of imitators.

Google and most other web engines utilize not only PageRank but more than 150 criteria to determine relevancy. The algorithm "remembers" where it has been and indexes the number of cross-links and relates these into groupings. PageRank is based on citation analysis that was developed in the 1950s by Eugene Garfield at the University of Pennsylvania. Google's founders cite Garfield's work in their original paper. In this way virtual communities of webpages are found. Teoma's search technology uses a communities approach in its ranking algorithm. NEC Research Institute has worked on similar technology. Web link analysis was first developed by Jon Kleinberg and his team while working on the CLEVER project at IBM's Almaden Research Center. Google is currently the most popular search engine.

Yahoo! Search

The two founders of Yahoo!, David Filo and Jerry Yang, Ph.D. candidates in Electrical Engineering at Stanford University, started their guide in a campus trailer in February 1994 as a way to keep track of their personal interests on the Internet. Before long they were spending more time on their home-brewed lists of favourite links than on their doctoral dissertations. Eventually, Jerry and David's lists became too long and unwieldy, and they broke them out into categories. When the categories became too full, they developed subcategories ... and the core concept behind Yahoo! was born. In 2002, Yahoo! acquired Inktomi and in 2003, Yahoo! acquired Overture, which owned AlltheWeb and AltaVista. Despite owning its own search engine, Yahoo! initially kept using Google to provide its users with search results on its main website Yahoo.com. However, in 2004, Yahoo! launched its own search engine based on the combined technologies of its acquisitions and providing a service that gave pre-eminence to the Web search engine over the directory.

Service scope

The scopes of hosting services vary widely. The most basic is webpage and small-scale file hosting, where files can be uploaded via File Transfer Protocol (FTP) or a Web interface. The files are usually delivered to the Web "as is" or with little processing. Many Internet service providers (ISPs) offer this service for free to their subscribers. People can also obtain Web page hosting from other, alternative service providers. Web page hosting is typically free, advertisement-sponsored, or cheap.

Web page hosting is generally sufficient only for personal web pages. A complex site calls for a more comprehensive package that provides database support and application development platforms (e.g. PHP, Java, and ASP.NET). These facilities allow the customers to write or install scripts for applications like forums and content management. For e-commerce, SSL is also required.

The host may also provide a Web interface control panel (e.g. cPanel, Hosting Controller, Plesk or others) for managing the Web server and installing scripts as well as other services like e-mail. Control panels and web interfaces have been causing some controversy lately as Web.com claims that it holds patent rights to the hosting technology with its 19 patents. Hostopia, a large wholesale host, recently purchased a license to use that technology from web.com for 10% of retail revenues. Web.com recently sued Go Daddy as well for similar patent infringement.

Some hosts specialize in certain software or services (e.g. e-commerce). They are commonly used by larger companies to outsource network infrastructure to a hosting company. To find a web hosting company, there are searchable directories that can be used.

Web hosting service

A web hosting service is a type of Internet hosting service that allows individuals and organizations to provide their own websites accessible via the World Wide Web. Web hosts are companies that provide space on a server they own for use by their clients as well as providing Internet connectivity, typically in a data center. Webhosts can also provide data center space and connectivity to the Internet for servers they do not own to be located in their data center, called colocation.

How the Web works

Viewing a Web page or other resource on the World Wide Web normally begins either by typing the URL of the page into a Web browser, or by following a hypertext link to that page or resource. The first step, behind the scenes, is for the server-name part of the URL to be resolved into an IP address by the global, distributed Internet database known as the Domain name system or DNS. The browser then establishes a TCP connection with the server at that IP address.

The next step is for an HTTP request to be sent to the Web server, requesting the resource. In the case of a typical Web page, the HTML text is first requested and parsed by the browser, which then makes additional requests for graphics and any other files that form a part of the page in quick succession. When considering web site popularity statistics, these additional file requests give rise to the difference between one single 'page view' and an associated number of server 'hits'.

The Web browser then renders the page as described by the HTML, CSS and other files received, incorporating the images and other resources as necessary. This produces the on-screen page that the viewer sees.

Most Web pages will themselves contain hyperlinks to other related pages and perhaps to downloads, source documents, definitions and other Web resources.

Such a collection of useful, related resources, interconnected via hypertext links, is what has been dubbed a 'web' of information. Making it available on the Internet created what Tim Berners-Lee first called the WorldWideWeb