The Rapid Service/Prediction Center of the International Earth Rotation and Reference Systems Service (IERS), located at the U.S. Naval Observatory (USNO), monitors the Earth's orientation and disseminates this information to many organizations on a continuous basis. Geodetic Very Long Baseline Interferometry (VLBI) is a space-based technique which allows for accurate measurement of the Earth and its orientation in inertial space. An inertial frame is defined by compact radio sources, billions of light years from Earth, called quasars. The Earth’s orientation in this inertial reference frame is measured. The quasars are observed with a global network of radio telescopes. Telescopes in the network simultaneously record signals from quasars together with signals from local atomic clocks onto hard disks. At the correlator, data are played back to determine differential time delays. From these differences in arrival times of signals at the various telescopes, the baselines between the telescopes can be determined with an accuracy of a few millimetres. In addition, VLBI data allows us determine the CRF and TRF and to measure Earth orientation parameters (EOP) as well as tropospheric parameters.
115 NAVY SPACE EIDWS TRAINING IT1(IDW/SW) Beall
115.1 Describe the following Space mission areas:[ref. a]
a. Space Force Enhancement.
Space force enhancement contributes to the establishment and maintenance of a space Common Operational Picture (COP), which is critical to carrying out simultaneity and depth in joint operations.
b. Space Support.
Operations to deploy and sustain military and intelligence systems in space.
c. Space Control.
Operations to ensure freedom of action in space for the US and its allies and, when directed, deny an adversary freedom of action in space.
d. Space Force Application.
Combat operations in, through, and from space to influence the course and outcome of conflict.
115 NAVY SPACE 115.2 a. The Sun. [ref. b] The sun has the biggest effect on the space environment. Fueled by nuclear fusion, the sun combines or “fuses” 600 million tons of hydrogen each second. Two by-products of the fusion process that impact space systems are: Electromagnetic Radiation and Electrically Charged Particles.
115 NAVY SPACE 115.2 b. Solar Wind. [ref. b] Solar wind is electrically charged particles that stream continuously from the Sun. This excited state of atmospheric molecules degrades radar performance in the auroral zones, including ballistic missile warning radar. It can also adversely affect satellites at altitudes to 600 miles, to include polar orbiting satellites.
115 NAVY SPACE 115.2 c. Solar Cycle. [ref. b] Solar activity is cyclic in nature, following an 11-year cycle which is called the Solar Cycle. Generally there is a 4-year rise to a solar maximum, followed by a gradual 7-year decline to solar minimum.
115 NAVY SPACE Largest Solar Flare on record. Off the chart coronal mass ejection.
115.2 Describe the Space environment to include the following. (CONTINUED)[ref. b]
d. Van Allen Radiation Belts.
The Outer and Inner Van Allen Radiation Belts are two concentric, donut-shaped regions of stable, trapped charged particles that exist because the geomagnetic field near the Earth is strong and field lines are closed. The inner belt is about 5000km above Earth’s surface and the outer belt is about 16,000km-20,000km above Earth’s surface. Communications satellites in “Geosynchronous” orbit (35,782 km or 22,235 statute miles altitude) suffer whenever the Van Allen belt moves inward or outward. Satellites in a semi-synchronous orbit such as GPS satellites suffer from a variable, high-density particle environment.
e. Atmospheric Drag.
Another source for space object positioning errors is that of atmospheric drag on low orbiting objects (less than 1,000-km altitude). Energy deposited in the Earth’s upper atmosphere by charged particle bombardment heats the atmosphere, causing it to expand outward over a period of time. This produces more frictional drag on a satellite than expected and decreases its altitude while increasing its speed.
115 NAVY SPACE VAN ALLEN RADIATION BELTS ATMOSPHERIC DRAG
A satellite is considered to be in a low earth orbit (LEO) at altitudes between approximately 100 and 420 miles above the Earth's surface. Between these altitudes the satellite will have an orbital period from 87.5 – 110 min. The Space Shuttle and some scientific satellites are typically placed in low inclination, low earth circular orbits.
b. Medium Earth Orbit.
A satellite is considered to be in medium earth orbit (MEO) at altitudes between approximately 450 and 10,000 miles above the Earth’s surface. Between these altitudes the satellite will have an orbital period from 110 min. – 12 hours. This is the typical orbit of all Global Positioning Satellites (GPS.)
c. Highly Elliptical Orbit.
To obtain satellite communications capability in the northern or southern latitudes, a highly eccentric elliptical orbit, commonly referred to as a Molniya orbit is used. The Molniya orbit has an apogee nearly equivalent to the geosynchronous altitude and an inclination of approximately 63° to 64°. A satellite in this type of highly eccentric elliptical orbit slows down at apogee in the Northern Hemisphere (providing longer duration over its greatest field of view) and whips through perigee (smallest field of view) in the Southern Hemisphere.
115.3 Identify the following orbits: (CONTINUED)[ref. b]
d. Geosynchronous Orbit.
A satellite placed in orbit with an average altitude of approximately 19,300 nautical miles (nm) will have an average angular velocity exactly equal to that of the Earth's. Stated more simply, the satellite would have a period approximately equal to one day (24 hours.) This is the typical orbit of most communications satellites, (i.e. MILSTAR, UFO-E/EE, CWSP, DSCS)
e. Polar Orbit.
In contrast to a low inclination orbit and its latitude limitations, a polar orbit passes over the entire surface of the Earth. A polar orbit has an inclination of 90° and is usually circular. Due to the ability to pass over the entire surface of the earth throughout the course of several days, the polar orbit is used extensively by imagery satellites.
115 NAVY SPACE POES 115.3 (CONT.) Polar Orbiting Environmental Satellites (POES) are two polar-orbiting satellites constantly circling the Earth in an almost north-south orbit, passing close to both poles.
115.6 Discuss the following Military Satellite Communication Systems:[ref. b]
a. Navy UHF Follow-on.
The Navy has procured a new constellation of satellites to replace the aging FLTSAT program: the UHF Follow-On (UFO-E (EHF) and UFO-EE (Enhanced EHF)), which includes UFO-E 4-6 and UFO-EE 7-11. UFO-EE 8 and 10 are GBS capable satellites. UFO-EE 9 is no longer in service. The UFO features higher power transmitters designed to improve service, reliability, and dependability in the UHF and EHF spectrums. The UFO satellites are mixed with the FLTSATCOM legacy system.
b. Defense Satellite Communications System.
The Defense Satellite Communications System (DSCS) is a high capacity, SHF satellite based subsystem of the Defense Communications System (DCS). The DCS provides worldwide, jam-resistant, secure voice and high data rate communications for command and control, crises management, and intelligence data transfer service between the National Command Authority, Joint Chiefs of Staff (NCA/JCS) and the Unified Commanders-in-Chief (CINC).
115.6 Discuss the following Military Satellite Communication Systems:(CONT.)[ref. b]
c. Global Broadcast Service.
The Global Broadcast Service (GBS) is derived from commercial direct broadcast technology and uses high-powered transponders to provide HDR wideband simplex broadcast signals into 1-meter or smaller antennas and sophisticated receiver suites. The GBS payload revolutionized satellite communications by providing high-volume data and video information products to military tactical terminals. Naval Space Command has been designated the manager for GBS on UFO satellites and ensures the GBS payload is optimally configured to support the Joint user community.
d. Wideband Gapfiller System.
The Wideband Gapfiller satellites will be the DoD’s most capable and powerful communication satellite. The WGS will provide near-term continuation and augmentation of the services currently provided by the Defense Satellite Communications System (DSCS) and the Global Broadcast Service (GBS) Ka services currently provided by GBS payloads on UFO satellites. WGS is a high-capacity satellite communications system designed to support the warfighter with newer and far greater capabilities than those provided by current systems, yet it is compatible with existing control systems and terminals.
115 NAVY SPACE DSCS UFO with GBS payload UFO-E/EE WGS
115.8 Describe the advantages and disadvantages of Space-based Intelligence, Surveillance and Reconnaissance (ISR).[ref. a]
Space-based ISR is a part of the synchronization and integration of sensors, assets, and processing, exploitation, and dissemination systems for collection of data and information on an object or in an AOI on a persistent, event driven, or scheduled basis.
Intelligence : The product resulting from the collection, processing, integration, evaluation, analysis, and interpretation of available information concerning foreign nations, hostile or potentially hostile forces or elements, or areas of actual or potential operations.
Surveillance : Space systems can provide commanders with systematic observation of aerospace, surface, or subsurface areas, places, persons, or things by visual, electronic, photographic, or other means that provide commanders with situational awareness within a given area.
Reconnaissance : Reconnaissance is a mission undertaken to obtain, by visual observation or other detection methods, information about activities and resources of an enemy or adversary, or to secure data concerning the meteorological, hydrographic, or geographic characteristics of a particular area.
115.8 Describe the advantages and disadvantages of Space-based Intelligence, Surveillance and Reconnaissance (ISR).(CONTINUED)[ref. a]
Advantages : The prime advantage of space-based ISR capabilities is their potential to provide systematic and focused coverage of Areas of Interest (AOI), sometimes without detection, from sanction.
Disadvantages : In addition to the access limitations and a predictable overflight schedule dictated by the satellite orbit, satellite systems may be affected by a variety of atmospheric disturbances such as fog, smoke, electrical storms, and precipitation and clouds, which affect the ability of imaging systems to detect adversary activity, missile launches, and battle damage.
115.9 Discuss Space Situational Awareness.[ref. a]
The requisite current and predictive knowledge of the space environment and the operational environment upon which space operations depend – including physical, virtual, and human domains – as well as all factors, activities, and events of friendly and adversary space forces across the spectrum of conflict.
Currently over 17,000 satellites orbiting Earth. SSA
A branch of astronomy that deals with measurements (as of positions and movements) of celestial bodies. This will translate into enhanced pointing accuracies for satellites and improved navigation for space vehicles established in Geosynchronous (GEO) or Highly Elliptical Earth Orbits (HEO).
The term "Earth orientation" refers to the direction in space of axes which have been defined on the Earth. It is usually measured using five quantities: two angles which identify the direction of the Earth's rotation axis within the Earth, an angle describing the rotational motion of the Earth, and two angles which characterize the direction of the Earth's rotation axis in space. With these coordinates, the orientation of the Earth in space is fully described.
115.11 a. Global Positioning System (GPS).[ref. c]
Precise Time and Time Interval (PTTI) and ensuring uniformity in PTTI operations. Coordinated Universal Time (UTC) (USNO), as determined by the Master Clock at USNO, is the DOD time standard. The output of the Master Clock is the reference for the master control of GPS.
Geo-location is closely related to positioning but can be distinguished from it by a greater emphasis on determining a meaningful location rather than just a set of geographic coordinates. Specifically this involves the use of advanced RF location systems utilizing, for example, Time Difference Of Arrival ( TDOA ) where greater specificity of location is possible. Precise timing provided by U.S. Naval Observatory aides in determining geo-location for naval sea and shore assets.
Computer network time synchronization is a system of distributed network time servers that provide an accurate and reliable time synchronization service for computers on the Internet and the Secret Internet Protocol Router Network (SIPRNet). Network time transfer is achieved by robust estimation between remote systems of clock offset, network delays, and network dispersion. Network time synchronization over the non-deterministic Internet is maintained at the millisecond level.