Browse Definitions:
Definition

perigee

When a satellite follows a non-circular orbit around the earth, the satellite's path is an ellipse with the center of the earth at one focus. Such a satellite has variable altitude and variable orbital speed. The point of lowest altitude is called perigee. The term also applies to the minimum distance in kilometers or miles between the satellite and the center of the earth. (Perigee can be measured between the satellite and the earth's surface, although this is a less precise specification because the earth is not a perfect sphere. The difference is approximately 4,000 miles or 6,400 kilometers.)

/WhatIs/images/perigee.gif (2711 bytes)

At perigee, a satellite travels faster than at any other point in its orbit. When viewed from the earth's surface, a satellite at or near perigee traverses the sky at a rapid pace. In communications, perigee is the least desirable time to access a satellite. Although its proximity means that the signal path is short, the fact that the satellite is rapidly moving means that it is accessible for only a brief time. In addition, if a directional antenna is used at a ground-based station, it is difficult to track the satellite because the position of the antenna(azimuth and elevation) must be constantly and rapidly adjusted.

One of the principal advantages of a geostationary satellite is the fact that it follows a circular orbit, so the orbital speed is constant. In addition, the satellite's synchronization with the earth's orbit means that the antenna of an earth-based station can be pointed at a fixed spot in the sky, and no further adjustment of antenna orientation is needed.

Compare apogee .

This was last updated in June 2010

Start the conversation

Send me notifications when other members comment.

By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

Please create a username to comment.

-ADS BY GOOGLE

File Extensions and File Formats

SearchCompliance

  • internal audit (IA)

    An internal audit (IA) is an organizational initiative to monitor and analyze its own business operations in order to determine ...

  • pure risk (absolute risk)

    Pure risk, also called absolute risk, is a category of threat that is beyond human control and has only one possible outcome if ...

  • risk assessment

    Risk assessment is the identification of hazards that could negatively impact an organization's ability to conduct business.

SearchSecurity

  • security information and event management (SIEM)

    Security information and event management (SIEM) is an approach to security management that seeks to provide a holistic view of ...

  • polymorphic virus

    A polymorphic virus is a harmful, destructive or intrusive type of malware that can change or 'morph,' making it difficult to ...

  • cyberterrorism

    According to the U.S. Federal Bureau of Investigation, cyberterrorism is any 'premeditated, politically motivated attack against ...

SearchHealthIT

  • accountable care organization (ACO)

    An accountable care organization (ACO) is an association of hospitals, healthcare providers and insurers in which all parties ...

  • patient engagement

    Patient engagement is an ideal healthcare situation in which people are well-informed about -- and motivated to be involved -- in...

  • personal health record (PHR)

    A personal health record (PHR) is a collection of health-related information that is documented and maintained by the individual ...

SearchDisasterRecovery

  • business continuity and disaster recovery (BCDR)

    Business continuity and disaster recovery (BCDR) are closely related practices that describe an organization's preparation for ...

  • business continuity plan (BCP)

    A business continuity plan (BCP) is a document that consists of the critical information an organization needs to continue ...

  • call tree

    A call tree -- sometimes referred to as a phone tree -- is a telecommunications chain for notifying specific individuals of an ...

SearchStorage

SearchSolidStateStorage

  • hybrid hard disk drive (HDD)

    A hybrid hard disk drive is an electromechanical spinning hard disk that contains some amount of NAND Flash memory.

Close