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MESSENGERabbrev. for Mercury Surface, Space Environment, Geochemistry, and Ranging, a NASA mission to the planet Mercury, launched Aug. 3 2004 from Cape Canaveral by a Delta 2 Heavy rocket and forming part of the agency's Discovery Program. Although an acronym, the name recalls the planet's mythical association with Mercury the winged messenger of the gods. The MESSENGER spacecraft is NASA's first Mercury orbiter. Its chief goal is to investigate important scientific questions about Mercury's surface and interior composition and its environment. Among other things, the probe will seek to find out why Mercury's density is so high, what the composition and structure of its crust is, and whether there has been any volcanism. It will also look into the nature, dynamics and origin of Mercury's magnetic field (possibly driven by a liquid outer core) and its tenuous atmosphere. One focus of interest will be the mysterious polar deposits on Mercury, which some scientists believe could be water ice. The data for these questions will be gathered by an array of seven miniature instruments working in one of the most hostile environments in the Solar System, a mere 58 million km from the Sun.
To avoid overshooting its target and possibly falling into the Sun, the MESSENGER craft is following a 6½-year, 7.9-billion-km roundabout course to Mercury that should slow it down sufficiently to accomplish its task. The journey will involve 15 solar orbits, 6 trajectory-altering planetary flybys (including 1 of the Earth, 2 of Venus, and 3 of Mercury itself), and 6 crucial rocket firings. It will enter orbit around Mercury in March 2011 for a year of scientific data collection.
AIM(1) (AOL Instant Messenger) America Online's instant messaging service, which supported text chat, photo sharing, online gaming and PC to PC voice. An AIM list of Instant Messenger contacts was called a "Buddy List." AIM was part of America Online and then a stand-alone service in 1997 but was discontinued at the end of 2017. See instant messaging and AOL.
(2) (Application Integration Middleware) An umbrella term for middleware software that ties applications together. See application integration, middleware and PPMW.
(3) (Association for Automatic Identification and Mobility, Warrendale, PA, www.aimglobal.org) The trade association for the automatic identification and data capture (AIDC) industry. Established in 1982 as a product division of the Material Handling Institute (MHI), AIM is involved in setting standards for barcodes, magnetic stripes and RFID technology. See also AIIM.
(4) (Apple IBM Motorola) The alliance of Apple, IBM and Motorola that developed the PowerPC chip. See PowerPC and Apple-IBM alliance.
Facebook MessengerFacebook's instant messaging service, which is available on the Facebook website and as an app for mobile devices. Introduced in 2011, and initially bundled into the Facebook mobile apps, instant messaging was separated into the stand-alone Messenger app in 2014. In addition, iPhone and Android users can use Messenger as their primary text messaging client (SMS) and not have to switch between apps for messages from non-Messenger users.
As of 2021, Facebook Messenger and Facebook's WhatsApp instant messaging exist as separate services, each with more than a billion users. See Chat Head, WhatsApp Messenger, Facebook M and Facebook.
Messenger Kids With Parental Controls
In 2017, Messenger Kids was introduced for children under the age of 13. Parents have to authorize its use and are in control of whom their children can text and chat with. Digital stickers and animated masks let kids create fun photos and videos.
Google TalkAn earlier instant messaging (IM) service from Google, introduced in 2005. Google Talk provided text messaging and voice calling for Windows, Android, BlackBerry and Chrome OS devices. Nicknamed "Gchat" and based on the XMPP/Jabber protocol (see Jabber), Google Talk provided a link to the user's Gmail account and displayed the number of unread messages in the inbox. It was also a component of the Google Apps package (see Google Workspace). In 2015, the Google Talk client programs were discontinued although third-party apps that use the XMPP protocol are still supported. See Google chat.
messaging systemA messaging system sends text messages from one user to one or more other users. Image attachments are also typically supported. This definition covers the components of an Internet-based email system. For text and instant messaging, see text messaging and instant messaging.
Mail User Agent (Client)
The mail user agent (MUA or UA) is the client email program, such as Outlook, Eudora or Mac Mail, which is used to compose, send and receive messages.
Message Transfer Agent (Server)
The message transfer agent (MTA), or "mail transfer agent," is a mail server that forwards messages from user agents (MUAs) or delivers mail to its own message store (MS) for local recipients. Sendmail and Microsoft Exchange are the most widely used MTAs, and in a large enterprise, there may be several MTAs deployed.
The message store (MS) holds the mail until it is selectively retrieved and deleted by an access server. A local delivery agent (LDA) writes the messages from the MTA to the message store, and the protocols used to retrieve the mail are POP and IMAP (see POP3 and IMAP4).
The Internet's SMTP
Internet email is based on the SMTP protocol. Prior to the Internet's enormous growth in the late 1990s, numerous proprietary messaging systems were widely used, including cc:Mail, Microsoft Mail, PROFS and DISOSS. See SMTP, messaging middleware, text messaging and instant messaging.
WhatsApp MessengerAn ad-free instant messaging service for all major smartphones from WhatsApp Inc., wholly owned by Facebook. Founded in 2009 by Brian Acton and Jan Koum, WhatsApp uses the Internet as an alternative to the SMS text messaging system. Via Wi-Fi, subscribers pay nothing for WhatsApp messages the first year and 99 cents per year thereafter. If Wi-Fi is unavailable, and people use their cellular data plans for WhatsApp messages, thousands can be sent for a fraction of total usage because text takes up very few bytes (characters).
WhatsApp also provides voice calling from one WhatsApp user to the other, as well as voice recording, which lets users record and send audio messages instead of typing.
With more than 400 million monthly users worldwide and billions of messages sent each day, Facebook acquired the company for USD $19 billion in 2014. See SMS and Facebook Messenger.