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
SearchCompliance
  • OPSEC (operations security)

    OPSEC (operations security) is a security and risk management process and strategy that classifies information, then determines ...

  • smart contract

    A smart contract is a decentralized application that executes business logic in response to events.

  • compliance risk

    Compliance risk is an organization's potential exposure to legal penalties, financial forfeiture and material loss, resulting ...

SearchSecurity
  • COBIT

    COBIT is an IT governance framework for businesses wanting to implement, monitor and improve IT management best practices.

  • security policy

    A security policy is a document that states in writing how a company plans to protect its physical and information technology (IT...

  • email spam

    Email spam, also known as junk email, refers to unsolicited email messages, usually sent in bulk to a large list of recipients.

SearchHealthIT
SearchDisasterRecovery
  • What is risk mitigation?

    Risk mitigation is a strategy to prepare for and lessen the effects of threats faced by a business.

  • change control

    Change control is a systematic approach to managing all changes made to a product or system.

  • disaster recovery (DR)

    Disaster recovery (DR) is an organization's ability to respond to and recover from an event that affects business operations.

SearchStorage
  • JBOD (just a bunch of disks)

    JBOD, which stands for 'just a bunch of disks,' is a type of multilevel configuration for disks.

  • bare-metal restore

    A bare-metal restore (also referred to as bare-metal recovery or bare-metal backup) is a data recovery and restoration process ...

  • mSATA SSD (mSATA solid-state drive)

    An mSATA SSD is a solid-state drive (SSD) that conforms to the mSATA interface specification developed by the Serial ATA (SATA) ...

Close