text: Army Space Operations Overview
  1-59. As an example, if the Earth were represented by a basketball, most LEO would be within one inch of
  the ball. A medium Earth orbit would be centered approximately 14.5 inches above the ball, and GEO would
  be 27 inches above the ball.
  1-60. While unfettered access to satellites in Earth orbit provides a tremendous advantage for information
  dissemination and collection, there are limitations. Spacecraft follow strict motion and orbital mechanic laws
  of physics. Revisit rates, coverage area, and dwell time over areas targeted for observation are functions of
  spacecraft orbits. For example, a highly elliptical orbit yields a long dwell time over large areas but is
  designed for only partial hemisphere access, while a LEO provides global access but a short access time.
  Generally, only minor changes to orbits are made after initial orbit insertion due to finite fuels onboard.
  1-61. Space-based sensors are vital to all phases of operations, and particularly in non-contiguous areas.
  Theater downlink and direct downlink are fundamental to timely, assured, and responsive support to the
  ground maneuver force. Space-based collection assets operate within established orbital paths. Changing the
  orbit requires time and the use of a limited propellant supply. Space-based assets are susceptible to threat
  denial and deception practices. Table 1-1 lists the characteristics or each orbit type.
  Table 1-1. Characteristics of satellite orbits
  Type Description Advantages Disadvantages Uses
  Low Earth • Circular shaped • Near Earth – high • Small coverage • Surveillance
  Orbit • Earth’s surface up resolution and area over Earth • Reconnaissance
  to ~1,600 km signal strength surface • Weather collection
  (1,000 miles) above • Limited time over
  • Human space flight
  Earth Earth’s surface
  (moves quickly)
  Medium • Circular shaped • Stable orbit • Highest radiation • Positioning,
  Earth • Between ~1,600- • Less signal level environment navigation, and
  Orbit 35,400 km (1,000- latency • Higher capacity timing
  22,000 miles) • Communication
  above Earth
  • GPS ~19,300 km
  (12,000 miles)
  above Earth
  Geo- • Circular shaped • Continuous • Far from Earth – • Communication
  synchrono • ~37,000 km coverage over resolution and • Surveillance
  us Earth (23,000 miles) specific area signal limitations • Reconnaissance
  Orbit above Earth • Coverage nearly • Easier to jam
  • Weather collection
  hemispheric • Signal latency
  • Missile warning
  Highly • Oval shaped • Long dwell time • Continuous • Communication
  Elliptical • Perigee: ~ 1000 km over a large area coverage requires over high latitudes
  Orbit (600 miles) • Coverage of high multiple satellites • Scientific
  • Apogee:~40,000 North or South • Surveillance
  km (25,000 miles) latitudes • Reconnaissance
  GPS - Global Positioning System km – kilometers
  1-62. A related limitation is predictability. The position of satellites in LEO may be accurately predicted.
  Predictions of satellite locations based on current orbit characteristics can be made weeks in advance. This
  predictability makes space-based information collection susceptible to camouflage, denial, and deception.
  Soldiers can use this information to their benefit when dealing with enemy capabilities—not considering
  such limitations could lead to unanticipated results. In addition to these limitations, many spacecraft are high-
  demand, low-density assets and may not be able to satisfy all demands. It is the responsibility of the space
  operations officer to ensure this information is known by the staff during mission planning.