Introduction Space Environment Orbit Foundation

Introduction and Brief History of Satellites

A satellite is any object that orbits another object (which is known as it is primary). All masses that are share of the solar system, including the Earth, are satellites either of the Sun, or satellites of those objects, such as the Moon. It is not always a simple matter to determine which is the ‘satellite’ in a pair of bodies. Because all objects exert gravity, the motion of the crucial object is likewise affected by the satellite. If two objects are ufficiently similar in mass, they are in general referred to as a binary system rather than a necessary object and satellite. The ordinary criterion for an object to be a satellite is that the center of mass of the two objects is inside the important object. In general usage, the term ‘satellite’ commonly refers to an artificial satellite (a man-made object that orbits the Earth or another body).

In May, 1946, the Preliminary Design of an Experimental World-Circling Spaceship stated, “A satellite vehicle with suitable instrumentation may be expected to be one of the most potent scientific tools of the Twentieth Century. The accomplishment of a satellite craft would invent repercussions comparable to the explosion of the atomic bomb…”

The space age begun in 1946, as scientists started out using captured German V-2 rockets to make measurements in the upper atmosphere. Before this period, scientists applied balloons that went up to 30 km and radio waves to study the ionosphere. From 1946 to 1952, upper-atmosphere exploration was conducted using V-2s and Aerobee rockets. This permitted measurements of atmospheric pressure, density, and temperature up to 200 km. The U.S. had been giving careful consideration to launching orbital satellites since 1945 under the Bureau of Aeronautics of the United States Navy. The Air Force’s Project RAND ultimately freed the above report, but did not believe that the satellite was a potential military weapon; rather they considered it to be a tool for science, politics, and propaganda. Following pressure by the American Rocket Society, the National Science Foundation, and the International Geophysical Year, military interest picked up and in early 1955 the Air Force and Navy were working on Project Orbiter, which involved using a Jupiter C rocket to launch a little satellite called Explorer 1 on January 31, 1958.

On July 29, 1955, the White House declared that the U.S. intended to launch satellites by the spring of 1958. This became known as Project Vanguard. On July 31, the Soviets declared that they intended to launch a satellite by the fall of 1957 and on October 4, 1957 Sputnik I was launched into orbit, which triggered the Space Race amid the two nations.

The biggest artificial satellite presently orbiting the world is the International Space Station, which may now and then be seen with the unaided humane eye.

Types of satellites

· Astronomical satellites: These are satellites used for observation of distant planets, galaxies, and other outer space objects.

· Communications satellites: These are artificial satellites stationed in space for the intents of telecommunications using radio at microwave frequencies. Most communications satellites use geosynchronous orbits or near-geostationary orbits, even though some recent systems use low Earth-orbiting satellites.

· Earth observation satellites are satellites specifically designed to detect Earth from orbit, similar to reconnaissance satellites but intended for non-military uses such as environmental monitoring, meteorology, map making etc. (See peculiarly Earth Observing System.)

· Navigation satellites are satellites which use radio time signals transmitted to enable mobile receivers on the ground to determine their precise location. The comparatively clear line of sight amid the satellites and receivers on the ground, combined with ever-improving electronics, allows satellite navigation schemes to measure emplacement to accuracies on the order of a few metres in real time.

· Reconnaissance satellites are Earth observation satellite or communications satellite deployed for military or intelligence applications. Little is known regarding the full power of these satellites, as governments who operate them normally keep selective information pertaining to their reconnaissance satellites classified.

· Solar power satellites are proposed satellites built in high Earth orbit that use microwave power transmission to beam solar power to very big antenna on Earth where it may be used in place of established power sources.

· Space stations are man-made structures that are designed for humane beings to live on in outer space. A space station is discerned from other manned spacecraft by it is lack of major propulsion or landing facilities — instead, other vehicles are employed as transport to and from the station. Space stations are designed for medium-term living in orbit, for periods of weeks, months, or even years.

· Weather satellites are satellites that principally are employed to monitor the weather and/or climate of the Earth.

· Miniaturized satellites are satellites of unusually low weights and little sizes. New classifications are used to categorize these satellites: minisatellite (500-200 kg), microsatellite (below 200 kg), nanosatellite (below 10 kg).

Orbit types

Many times satellites are characterized by their orbit. Although a satellite may orbit at closely any height, satellites are ordinarily categorized by their altitude:

· Low Earth Orbit (LEO: 200 – 1200km above the Earth’s surface)

· Medium Earth Orbit (ICO or MEO: 1200 – 35286 km)

· Geosynchronous Orbit (GEO: 35786 km above Earth’s surface) and Geostationary Orbit ( zero inclination geosynchronous orbit). These orbits are of queer interest for communication satellites and will be discussed in detail later.

· High Earth Orbit (HEO: above 35786 km)

The following orbits are particular orbits that are also applied to categorize satellites:

· Molniya orbits: Is a class of a highly elliptic orbit. A satellite placed in this orbit spends most of it is time over a indicated area of the earth, a phenomenon known as apogee dwell. Molniya orbits are named after a series of Soviet/Russian Molniya communications satellites that have been using this class of orbits since the mid 1960s.

· Heliosynchronous or sun-synchronous orbit: A heliosynchronous orbit, or more commonly a sun-synchronous orbit is an orbit in which an object always passes over any given point of the Earth’s surface at the same local solar time. This is a utile characteristic for satellites that effigy the earth’s surface in visible or infrared wavelengths (e.g. weather, spy and remote sensing satellites).

· Polar orbit : A satellite in a polar orbit passes above or closely above both poles of the planet (or other celestial body) on each revolution.

· Hohmann transfer orbit: For this queer orbit type, it is more mutual to distinguish the satellite as a spacecraft. In astronautics and aerospace engineering, the Hohmann transfer orbit is an orbital maneuver that moves a spacecraft from one orbit to another.

· Supersynchronous orbit or drift orbit : orbit above GEO. Satellites will drift in a westerly direction.

· Subsynchronous orbit or drift orbit: orbits close to but underneath GEO. Used for satellites undergoing station changes in an eastern direction.

Communication Satellites

A communications satellite (sometimes abbreviated to comsat) is an artificial satellite stationed in space for the purposes of telecommunications. Modern communications satellites use geosynchronous orbits, Molniya orbits or low Earth orbits.

For fixed services, communications satellites provide a engineering science complementary to that of fiber optic submarine communication cables. For mobile applications, such as communications to ships and planes satellite based communicationis only the viable means of communications as application of other technologies, such as cable, are impractical or impossible.

Early missions: The origin of satellite communicating may be traced to an article written by Arthur C. Clarke in 1945. He suggested that a radio relay satellite in an equatorial orbit with a amount of time of 24 hours would stay stationary with respect to earth’s surface and may be used for long-range radio communication, as it will over come the limitations imposed by world curvature. Sputnik 1, The world’s initial artificial (non communication) satellite, was launched on October 4, 1957. The primary satellite to relay communications was Project SCORE in 1958, which used a tape recorder to store and forward voice messages. It was employed to send a Christmas greeting to the world from President Eisenhower. NASA launched an Echo satellite in 1960. This 100-foot aluminized Mylar balloon served as a passive reflector for radio communications. Courier 1B, (built by Philco) also was launched in 1960, was the world’s firstborn active repeater satellite. Given underneath are the details of mileposts in satellite communcation history: -

· Herman Potocnik – describes a space station in geosynchronous orbit – 1928

· Arthur C. Clarke – proposes a station in geosynchronous orbit to relay communications and broadcast television – 1945

· Project SCORE – firstborn communications satellite – 1958

· Echo I – introductory passive reflector satellite – August 1960

· Courier 1B – introductory active repeater satellite – October 1960

· Telstar – the introductory active direct relay satellite designed to transmit television and high-speed data communications. Telstar was placed in an elliptical orbit (completed once each 2 hours and 37 minutes), rotating at a 45° angle above the equator. July 1962

· Syncom – firstborn communications satellite in geosynchronous orbit. Syncom 2 revolved around the world once per day at neverending speed, but because it still had north-south motion special instrumentation was necessitated to track it. 1963

· OSCAR-III – initial novice radio communications satellite – March 1965

· Molniya – firstborn Soviet communicating satellite, highly elliptic orbit – October 1965

· Early Bird – INTELSAT’s firstborn satellite for mercantile service – April 1965

· Orbita – basi national TV network based on satellite television – November 1967

· Anik 1 – the firstborn national satellite television system, Canada, – 1973

· Westar 1, the USA’s initial geosynchronous communications satellite – April 1974

· Ekran – primary serial Direct-To-Home TV communicating satellite 1976

· Palapa A1 – firstborn Indonesia communications satellite – July 8 1976

· TDRSS – basi satellite designed to provide communications relay services for other spacecraft. – 1983

· Mars Global Surveyor – firstborn communications satellite in orbit around another planet (Mars) – 1997

· Cassini spacecraft relays to Earth images from the Huygens probe as it lands on Saturn’s moon, Titan, the longest relay to date. — January 14, 2005

Depending on the need the communicating satellites may be placed in respective types of orbits. We talk about few mutual types: -

(a) Geostationary orbits Satellites: A satellite in a geostationary orbit appears to be in a fixed position to an earth-based observer. A geostationary satellite revolves around the world at a neverending speed once per day over the equator. The geostationary orbit is utile for communications apps because ground based antennae, which ought to be directed toward the satellite, may operate efficaciously without the need for highpriced instrumentation to track the satellite’s motion. Especially for apps that require a big number of ground antennae (such as direct TV distribution), the savings in ground instrumentation may more than warrant the extra cost and onboard complexity of lifting a satellite into the comparatively high geostationary orbit.

The conception of the geostationary communications satellite was initial proposed by Arthur C. Clarke, building on work by Konstantin Tsiolkovsky and on the 1929 work by Herman Potočnik (writing as Herman Noordung) Das Problem der Befahrung des Weltraums – der Raketen-motor. In October 1945 Clarke published an article titled “Extra-terrestrial Relays” in the British magazine Wireless World. The article described the fundamentals behind the deployment of artificial satellites in geostationary orbits for the intention of relaying radio signals. Thus Arthur C. Clarke is often times cited as being the inventor of the communications satellite.

The primary geostationary communications satellite was Anik 1, a Canadian satellite launched in 1972. The United States launched their own geostationary communication satellites afterward, with Western Union launching their Westar 1 satellite in 1974, and RCA Americom (later GE Americom, now SES Americom) launching Satcom 1 in 1975.

It was Satcom 1 that was instrumental in helping early cable TV channels such as WTBS (now TBS Superstation), HBO, CBN (now ABC Family), and The Weather Channel become successful, because these channels propagated their programming to all of the local cable TV headends using the satellite. Additionally, it was the primary satellite used by broadcast TV networks in the United States, like ABC, NBC, and CBS, to disseminate their programming to all of their local affiliate stations. The reason that Satcom 1 was so widely used is that it had twice the communications capacity of Westar 1 (24 transponders as opposed to Westar 1′s 12), which resulted in lower transponder usage costs.

By 2000 Hughes Space and Communications (now Boeing Satellite Systems) had built almost 40 percent of the satellites in service worldwide. Other major satellite manufacturers include Space Systems/Loral, Lockheed Martin (owns former RCA Astro Electronics/GE Astro Space business), Northrop Grumman, Alcatel Space and EADS Astrium.

(b) Low-Earth-orbiting satellites: A low Earth orbit quintessentially is a circular orbit with regards to 150 kilometers above the earth’s surface and, correspondingly, a amount of time (time to revolve around the earth) of when it comes to 90 minutes. Because of their low altitude, these satellites are only visible from within a radius of roughly 1000 kilometers from the sub-satellite point. In addition, satellites in low world orbit change their position relative to the ground position quickly. So even for local applications, a huge number of satellites are necessitated if the mission requires uninterrupted connectivity.

Low world orbiting satellites are less highpriced to position in space than geostationary satellites and, because of their closer proximity to the ground, require lower signal strength. So there is a trade off amongst the number of satellites and their cost. In addition, there are indispensable deviations in the onboard and ground instrumentation necessitated to support the two types of missions.

A group of satellites working in concert therefore is known as a satellite constellation. Two such constellations which were intended for provision for hand kept telephony, primarily to remote areas, were the Iridium and Globalstar. The Iridium scheme has 66 satellites. Another LEO satellite constellation, with backing from Microsoft enterpriser Paul Allen, was to have as a heap of as 720 satellites. It is also possible to offer discontinuous coverage using a low Earth orbit satellite competent of storing data received while passing over one portion of Earth and transmitting it later while passing over another part. This will be the case with the CASCADE system of Canada’s CASSIOPE communications satellite.

(c) Molniya satellites: As mentioned, geostationary satellites are constrained to operate above the equator. As a consequence, they are not always suitable for supplying services at high latitudes: for at high latitudes a geostationary satellite may appear low on (or even below) the horizon, affecting connectivity and causing multipathing (interference caused by signals reflecting off the ground into the ground antenna). The basi satellite of Molniya series was launched on April 23, 1965 and was used for experimental transmission of TV signal from Moscow uplink station to downlink stations, located in Russian Far East, in Khabarovsk, Magadan and Vladivostok. In November of 1967 Soviet engineers produced a distinctive scheme of national TV network of satellite television, called Orbita that was based on Molniya satellites.

Molniya orbits may be an likeable substitute in such cases. The Molniya orbit is highly inclined, guaranteeing good elevation over chosen positions for the duration of the northern share of the orbit. (Elevation is the extent of the satellite’s position above the horizon. Thus a satellite at the horizon has zero elevation and a satellite directly overhead has elevation of 90 degrees). Furthermore, the Molniya orbit is so designed that the satellite spends the outstanding majority of it is time over the far northern latitudes, for the duration of which it is ground footprint moves only slightly. Its amount of time is one half day, so that the satellite is available for operation over the purposed region for eight hours each second revolution. In this way a constellation of three Molniya satellites (plus in-orbit spares) may provide ceaseless coverage.

Molniya satellites are specifically employed for telephony and TV services over Russia. Another application is to use them for mobile radio schemes (even at lower latitudes) since cars journeying through urban areas need access to satellites at high elevation in order to secure good connectivity, e.g. in the presence of tall buildings.

Applications of Satellites

(a) Telephony: One of the major apps of a communicating satellite is in provision of long distance telephone services. The connectivity is through frequency division multiple access (FDMA) or time division multiple access(TDMA) predominantly. Telephone subscribers may be connected through a network of exchanges which are in turn connected to satellite world stations which uplink the traffic to satellite for further processing.

(b) Television and Radio: There are two types of satellites used for television and radio:

(i) Direct Broadcast Satellite (DBS): A direct broadcast satellite is a communications satellite that transmits to little DBS satellite dishes (usually 18″ to 24″ in diameter). Direct broadcast satellites in general operate in the upper part of the Ku band. DBS engineering science is applied for DTH-oriented (Direct-To-Home) satellite TV services, such as DirecTV and Dish Network in the United States, ExpressVu in Canada, and Sky Digital in the UK.

(ii) Fixed Service Satellite (FSS): Use the C band, and the lower portions of the Ku bands. They are normally applied for broadcast feeds to and from television networks and local affiliate stations (such as program feeds for network and syndicated programming, live shots, and backhauls), as well as being used for distance learning by schools & universities, business television (BTV), videoconferencing, and frequent mercantile telecommunications. FSS satellites are likewise used to disseminate national cable channels to cable TV headends. FSS satellites differ from DBS satellites in that they have a lower RF power output than the latter, calling for a much more prominent dish for reception (3 to 8 feet in diameter for Ku band, and 12 feet on up for C band). FSS satellite engineering science was likewise in the first place applied for DTH satellite TV from the late 1970s to the early 1990s in the USA in the form of TVRO (TeleVision Receive Only) receivers and dishes (a.k.a. big-dish, or more pejoratively known as huge ugly dish, systems). It was also applied in it is Ku band form for the now-defunct Primestar satellite TV service.

(c) Mobile satellite technologies: Initially available for broadcast to stationary TV receivers, by 2004 frequent mobile direct broadcast apps made their aspect with that arrival of two satellite radio systems in the United States: Sirius and XM Satellite Radio Holdings. Some manufacturers have also introduced special antennas for mobile reception of DBS television. Using GPS engineering as a reference, these antennas mechanically re-aim to the satellite no matter where or how the vehicle (that the antenna is mounted on) is situated. These mobile satellite antennas are frequent with some recreational vehicle owners. Such mobile DBS antennas are also used by JetBlue Airways for DirecTV (supplied by LiveTV, a subsidiary of JetBlue), which passengers may view on-board on LCD screens mounted in the seats.

(d) Amateur radio: Amateur radio operators have access to the OSCAR satellites that have been designed specifically to carry novice radio traffic. Most such satellites operate as space borne repeaters, and are in general accessed by amateurs equipped with UHF or VHF radio instrumentation and highly directional antennas such as Yagis or dish antennas. Due to the limitations of ground-based novice equipment, most novice satellites are launched into reasonably low Earth orbits, and are designed to deal with only a fixed number of brief contacts at any given time. Some satellites also provide data-forwarding services using the X.25 or similar protocols.

Satellite Broadband Services: In recent years, satellite communicating engineering science has been applied as a means to connect to the Internet by way of broadband selective information connections. This is may be very utile for users to test who are located in very remote areas, and can’t access a wireline broadband or dialup connection.

Countries with satellite launch capability

This list includes regions with an independent capability to place satellites in orbit, including production of the necessary launch vehicle. Many more countries have built satellites that were launched with the aid of others. The French and British capablenesses are now subsumed by the European Union beneath the European Space Agency.

First launch by country

Country Year of initial launch First satellite

Russia 1957 “Sputnik 1″

United States 1958 “Explorer 1″

France 1965 “Asterix”

Japan 1970 “Osumi”

China 1970 “Dong Fang Hong I”

United Kingdom 1971 “Prospero X-3″

European Union 1979 “Ariane 1″

India 1980 “Rohini”

Israel 1988 “Ofea 1″

Iran 2005 “Sina 1″

In 1998, North Korea claimed to have launched a satellite, but this was never confirmed, and widely believed to be a cover for the test launch of the Taepodong-1 missile over Japan (See Kwangmyongsong).

Introduction Space Environment Orbit Foundation

The all-new Kindle has a new electronic-ink screen with 50 percent better contrast than any other e-reader, a new sleek design with a 21 percent littler body while still keeping the same 6-inch-size reading area, and a 17 percent lighter weight at just 8.5 ounces. The new Kindle also offers 20 percent more immediate page turns, up to one month of battery life, double the storage to 3,500 books, built-in Wi-Fi, a graphite color option and more—all for only $139.

Introduction Space Environment Orbit Foundation Pic

Introduction Space Environment Orbit Foundation Picture

Introduction Space Environment Orbit Foundation Picture

Introduction Space Environment Orbit Foundation Pic

Most helpful client reviews

28344 of 28639 people found the following review helpful.
Kindle vs. Nook (updated 6/2/2011)
By Ron Cronovich
When I wrote this review last August, there was only one Nook, which is now called “Nook First Edition.” It proceeds to be available, but there are two new Nooks. The Nook Color was introduced last fall – it’s fundamentally a tablet computer, and runs the Android software that is ordinary on a heap of smartphones nowadays. It’s twice as heavy and costs twice as much as a Kindle, but equated to other tablet computers, it is a very good value.

And now (early June 2011), a new e-ink based Nook is coming out. It’s called the “Nook Simple Touch.” It is just now starting to ship, so plainly I don’t have one and can’t tell you anything when it comes to it that you can’t learn by reading online reviews. But the reviews are very favorable, so if you’re taking into account a Kindle, you ought to take a look at the new Nook Simple Touch, too.

But the Kindle is nonetheless still a compelling option. It’s a mature product, very well designed and easy to use, performance is very zippy, it’s competitively priced, and no e-ink based reader has a better, more readable display than the Kindle, not even the new Nook Simple Touch. Also, the Kindle universe is rather extensive: the Kindle store is great and has a heap of thousands of free e-books as well as good deals on most other e-books, and once purchased, you may read your Kindle books on closely any device you own (computer, phone, tablet), not just your Kindle. And there are tons of great cases and other accessaries for the Kindle.

So, while my review compares the Kindle to the older Nook, I’ll leave it here because it has a ton of selective information with regards to the Kindle, a great e-reader that deserves your attention, and because the initial Nook proceeds to be available. That said, I urge you to NOT buy the firstborn Nook. It was a respectable e-reader when it came out in 2009, and still had numerous value when I wrote when it comes to it in August 2010, but it is without doubt or question inferior by today’s standards.

———— my introductory review ————–

If you’re attempting to choose amid a Nook and a Kindle, perchance I may help. My wife and I have owned a Nook (the basi one), a Kindle 2, and a Kindle DX. When Amazon declared the Kindle 3 this summer, we pre-ordered two Kindle 3′s: the wi-fi only model in graphite, and the wi-fi + 3G model in white. They arrived in late August and we have used them very steadily since then. For us, Kindle is better than Nook, but Nook is a good device with it is own vantages that I will talk about below. I’ll end this review with a few words when it comes to the Nook Color.

First, reasons why we prefer the Kindle:

* Speed

In our experience, the Kindle is very zippy equated to the Nook. Page refresh speed (the time it takes a new page to appear after you push the page-turn button) was WAY rapidly and without delay on Kindle 2 than on Nook, and it’s quicker yet on Kindle 3. Yet, I read a whole book on the Nook and didn’t find the slower page refresh to be annoying – you get applied to it, and it’s not a problem.

For me, the more necessary speed divergence worries navigation – moving the cursor around the screen, for example to pick a book from your library, or to jump to a chapter by selecting it in the table of contents. On Kindle, you do this by pushing a 5-way rocker button, and the cursor moves very quickly. On Nook, you do this by activating the color LCD touchscreen (which normally shuts off when not in use, to conserve battery). A “virtual rocker button” appears on the screen, and you touch it to move the cursor. Unfortunately, the Nook cursor moves very sluggishly. This might not be a big deal to you, but it in truth got annoying to me, exceptionally since my wife’s Kindle was so quick and responsive.

In November 2010, Nook got a software upgrade that increments page refresh speed and makes navigation more responsive. I returned my Nook months ago, so I cannot tell you if the Nook’s performance is now equivalent to the Kindle’s, but Nook owners in the remarks division have convinced me that the software update improves the experience of using the Nook. If performance is a huge element in your decision, visit a Best Buy and compare Kindle and Nook side by side.

* Screen contrast

You’ve seen Amazon’s claims that the Kindle 3 e-ink has 50% better contrast than Kindle 2 or other e-ink devices. I have no way of precisely measuring the betterment in contrast, but I may tell you that the Kindle 3 display unquestionably has more contrast than Kindle 2 or Nook. The divergence is noticeable, and important: more screen contrast means less eyestrain when reading in poorly lit rooms.

In well-lit rooms, the Nook and Kindle 2 have sufficient contrast to concede for comfortable reading. But I often times read in low-light conditions, like in bed at night, or in a poorly lit room. In these situations, reading on Nook or Kindle 2 was a bit uncomfortable and often gave me a mild headache. When I got the Kindle 3, the extra contrast was without delay noticeable, and made it more comfortable to read beneath less-than-ideal lighting conditions. (If you go with a Nook, just make sure you have a good reading lamp nearby.)

* Battery life

The Nook’s color LCD touch screen drains it is battery quickly – I could never get more than 5 days out of a charge. The Kindle 2 had longer battery life than the Nook, and Kindle 3 has even longer life: in the 3 months since we received our Kindle 3′s, we specifically get 3 weeks of battery life amongst charges. (We keep wireless off with regards to half the time to save battery power.)

* Weight

Nook weighs regarding 3 ounces more than the new Kindle, and you may in truth feel the difference. Without a case, Nook is still light sufficient to hold in one hand for long reading sessions without fatigue. But in a case, Nook is a heavy sucker. The new Kindle 3 is so light, even in a case, we find it comfortable keeping in one hand for long reading sessions.

Reasons a great deal of people might prefer the Nook:

* In-store experience

If you need help with your nook, you may take it to any barnes and noble and get a real humane to help. You may take your nook into the coffee shop division of your local B&N store and read any book for free for up to one hour per day. When you take your nook to B&N, some in-store special deals and the occasional free book pop up on your screen.

* User-replaceable battery

Rechargeable batteries finally lose their capacity to hold a charge. Nook’s battery is user-replaceable and comparatively inexpensive. To replace Kindle’s battery, Amazon wants you to ship your Kindle to Amazon, and they will ship you back a DIFFERENT Kindle than the one you sent (it’s the same model, for example if you send a white Kindle 3, you get a white Kindle 3 back, but you get a “refurbished” one, NOT the precise one you sent them). I don’t like this at all.

However, assorted humans have posted remarks here that have eased my concerns. Someone looked up stats on the Kindle’s battery and did numerous simple calculations to show that it must last for 3 or more years. Before that happens, I will surely have upgraded to a newer Kindle model by then. Also, an individual found some companies that trade Kindle batteries at reasonable cost and have how-to videos that demonstrate how we may replace the battery ourselves. Doing this would void the Kindle’s warranty, but the battery will probably not fail until long after the warranty expires.

[update June 2011: The batteries in the Nook Color and Nook Simple Touch are not replaceable, but the battery in the initial Nook is.]

* ePub

Nook uses the ePub format, a widely employed open format. Amazon uses a proprietary ebook format. Many libraries will “lend” ebooks in the ePub format, which works with nook but not kindle. However, a free and reputable program called Calibre allows you to translate ebooks from one format to another – it supports a good deal of formats, including ePub and Kindle. The only catch is that it doesn’t work with copy-protected ebooks, so you can’t, for example, buy a Kindle book (which is copy protected) and translate it to ePub so you may read it on a Nook.

* Nook’s color LCD touchscreen

The introductory Nook has a little color LCD screen on the bottom for navigation. This could be a pro or con, depending on your preferences. It makes the Nook hipper and less drab than Kindle. Some persons take delight in using the color LCD to view their library or navigate. I did, at first. But after two weeks of use, and comparings with my wife’s Kindle, I found the committed buttons of the Kindle requiring little effort and far rapidly and without delay to use than the Nook’s color touchscreen. I also found the bright light from the color screen distracting when I was attempting to read a book or newspaper (though when not in use, it shuts off after a minute or so to conserve battery).

* expandable capacity

Nook comes with 2GB of internal memory. If you need more capacity, you may insert a microSD card to add up to 16GB more memory. Kindle comes with 4GB of internal memory – twice as much as Nook – but there’s no way to exaggerate that. Kindle doesn’t receive memory cards of any type. If you mainly use your device to read ebooks and newspapers, this shouldn’t be an issue. I have over 100 books on my Kindle, and I’ve employed only a tiny fraction of the memory. Once Kindle’s memory fills up, just delete books you don’t need prompt access to; you may always restore them later, in seconds, for free.

A few other notes:

Kindle and Nook have other features, such as an MP3 player and a web browser, but I caution you to have low expected values for these features. The MP3 player on the Kindle is like the first-generation iPod shuffle – you can’t see what song is playing, and you can’t navigate to other songs on your device. I don’t like the browser on either device; e-ink is just not a good engineering for surfing the web; it’s slower and clunkier than LCD screen technology, so even the browser on an Android phone or iPod touch is more gratifying to use. However, a lot of commenters have more favorable views of either device’s browser, and you might, too.

* ebook lending

If you have a Nook or a Kindle, you may “lend” an ebook you purchased to someone else with the same device for up to two weeks. The Nook has always had this feature. The Kindle just got this feature as of December 2010. Most but not all purchased ebooks are lendable, due to publisher restrictions.

* PDF aid

Kindle and Nook both handle PDF files, but in dissimilar ways. When you put a PDF file on your nook, nook converts it into an ebook-like file, then you may adjust the font size, and the text and pagination will adjust just like with any ebook. But you cannot see the basi PDF file in the native format in which it was created. Kindle 3 and Kindle DX have native support for PDF files. You may see PDF files just as they would appear on your computer. You may also convert PDF files to an ebook-like format, and then Kindle handles them just the way the Nook handles them – text and pagination adjust when you alter the font size. Unfortunately, numerous symbols, equations, and graphics get lost or mangled in the translation – even when watching PDF files in their native format on the Kindle. Moreover, the little screen size of the Kindle 3 and the Nook is not great for PDF files, most of which are designed for a larger page size. You may zoom and pan, but this is cumbersome and tiresome. Thanks to commenters who suggested looking at PDF files in landscape mode on the Kindle (I don’t recognise if you may do this on Nook); this way, you may see the entire top half of the page without panning, and then scroll down to the bottom half. This works a little better.

SUMMARY:

Nook and Kindle each offer their own advantages. We like the nook’s user-replaceable battery, compatibility with ePub format, and in-store experience. But we strongly prefer Kindle 3 because it is performance is zippier, it is higher-contrast screen is more comfortable to read, and it’s littler and lighter so it is more portable and more comfortable to hold in one hand for long reading sessions.

* Nook Color

Everything I wrote regarding the Nook in this review applies to the original Nook (which proceeds to be available), not the new Nook Color. To me, the Nook Color is in a dissimilar product category than the Kindle or original Nook. Nook Color has an LCD screen, like an iPad or most computer monitors. That’s a big disfavor for humans like me, who get headaches from reading a computer screen for long periods of time. Amazon’s Kindle product page has an informative division on e-ink vs. LCD displays.

But a lot of humans don’t have difficultnesses reading from computer screens, and the Nook Color is getting glowing reviews in the press and by owners. For the money, it offers a lot of functionality such as a good web browser and the capacity to play games and watch movies. But keep in mind: it costs a lot more than the Kindle, it weighs closely twice as much, it doesn’t come in a 3G version, and (unlike the primary Nook) the Nook Color doesn’t have a user replaceable battery.

2029 of 2065 persons found the following review helpful.
I Wanted a Dedicated E-Reader, and That’s What I Got
By Matthew E. Coenen
I’m a first-time Kindle owner, so I have not one thing to “compare” the latest Kindle to. I don’t own a Nook. I don’t own an iPad (and, in any case, that’s comparing apples to oranges). I don’t have a Sony e-reader. ‘

This will be a short, simple review.

I received my Kindle with regards to a week ago and haven’t been capable to put it down.

Things I like with regards to my Kindle?
1. The e-ink display is amazing.
2. Using the 5-way controller is simple and effective.
3. Page turn speeds are quicker than I thought they would be.
4. It’s lightweight, even with the attached cover (I have an Amazon cover with a built-in light)
5. Page-turning buttons are quiet and well-placed.
6. Recharge time is fast.
7. I may order a book and get started reading it in less than 60 seconds. Nice!
8. Portability… I may take 3,000 books with me when I travel for work and not require further and added suitcases or baggage fees.

Things I’m not too keen on?
1. Buttons are too close together and are laid out oddly.
2. Lack of person number buttons is frustrating.
3. Power button on the bottom? Not a bad thing. Just an odd thing. (Same for the headphone input). I commonly rest the “bottom” of a book on my lap when I read.

Things I hope modify in the future?
1. How books are organized… When I put a book in a collection (which is actually a “tag”), it still appears in the main list. It’s not genuinely “moved”, it’s plainly associated.
2. The look of the main screen. I’d like “folders” or a lot of other way to display “collections”.
3. Ability to manufacture personal “screen savers.”
4. E-book pricing, altho Amazon has little control over this. Still, most titles are the same price as or less than their hardback/paperback counterparts. (And I’m not opposed to paying more for comfortableness and portability).

Things that don’t bother me when it comes to other reviews?
1. The browser is experimental. Amazon has developed a consecrated e-reader, and it’s meant to be applied to read. Period. Not browse the web. If you want to browse the web, get a computer — not an e-reader.
2. The Kindle is not an mP3 player, either. Yes, it’s nice to have a heap of classical music playing in the background while I read, but I don’t need to see the title of the song, album art, etc. (And you may skip from track to track on the Kindle using shortcut keys).
3. Lack of a “color” or “touch” screen.

In summary, for $139, I’m rather thrilled with my buy and have arleady read multiple books on it. In fact, I think I’ve read more in the past week than I’ve read in the past month.

9299 of 9503 persons found the following review helpful.
Worth the money. Not perfect, but very very good for commence to finish novels in good light
By Jeffrey Stanley
The Kindle is my original e-ink reader. I own an iPad, an iPhone, and have owned a Windows-based phone in the past that I employed as an ereader.

My overall impression of the device is good.

The good:
I’d frankly rather read linear (read from page one to the end, one page at a time) fiction from it than a book, because I can’t always get comfortable with a book. Hardcovers are now and again a bit heavy, and paperbacks don’t always lie open easily. The Kindle is fantastically light and thin. I may hold it in one hand easily. The page turn buttons are conveniently located. Page-turns aren’t instant, but they’re in all likelihood rapidly and without delay than turning a physical page in a printed book (there are just a lot more page-turns unless you choose a little font). The contrast is better than other ereaders I’ve seen. There is zero eye strain in good light. My eyesight isn’t the greatest and I like being capable to increase the font size and read without glasses. I love being competent to browse the Kindle store and read samples before settling to purchase. The “experimental” browser is astoundingly usable, but isn’t great. It is utile for browsing wikipedia and blogs. The greatest drawback to the browser is the awkward pointer navigation, using the 5-way pad. It syncs your furthest read page over the internet so you may pick up where you left off using your iPhone or iPad.

The so-so:
The kindle store could use more categories and sorting options. You can’t sort by “top rated,” and there is no category for “alternate histories,” for example. Finding a very-specific type of fiction relies on keyword searches, which don’t do a great job. The wifi at times doesn’t connect before it times-out. You seldom need the wifi, but it is annoying if you modify a setting, answer “OK” to the prompt to connect, and the thing tells you it failed to connect two seconds later (the precise moment it gives evidence of that it did at long last connect, then you need to go back to update the setting again). Most settings don’t require a connection, but it is a minor annoyance. Most of your time will be expended reading, and of course your books are stored on the device and a connection is not required. Part of me wishes I’d purchased the 3G model, because the browser is good sufficient that having lifetime free 3G wireless would be worth the extra money. Magazines don’t look very good and are not very easy to navigate. There is minor glare in a lot of lighting conditions, for the most part when a lamp is positioned behind the reader’s head.

The bad:
The contrast is reasonable to poor in dim light. It is much posing no difficulty to read a printed page in dim light. In good light, contrast is on par with a pulp paperback. In dim light it feels closely like reading from an old Palm Pilot (resolution is better than an old Palm, but contrast is bad in dim light). The screen is little sufficient that the frequency of page turns is finelooking high. Even in good light, the light gray background is less pleasant than the eggshell background of a printed page. You ought to tell it to sync before you switch it off, if you suppose the feature permitting you to pick up where you left off using other gimmicks to work correctly. The copy shelter prevents you from using the files on anything other than Kindle software or devices.

Vs iPad:
IPad is a lot better for magazines, reference materials, and illustrated materials. Kindle is worlds better for reading novels. IPad is pretty heavy, making it more difficult to hold in your hand or carry with you everywhere. Kindle is much more portable and having little impact to hold. IPad has some awful children’s books and magazines, which take vantage of it is multimedia features. IPad is unreadable in sunlight and glare is bad in bright light. Kindle is as good as a printed page in bright light. Ipad serves as a originative tool, a computing tool, a gaming tool, and a communicating tool. Kindle is only a novel machine. I don’t regret buying either one of them. An iPad won’t replace books, but a Kindle can, if the book is text-only.

I highly commend this device at it is new low price if you are a usual reader of novels. I love my kindle. Just don’t suppose it to be more than it is. Leave the magazines and such to the tablet computers.

See all 27280 client reviews…