Space Technology

Meaning

• Technology that is related to entering, and retrieving objects or life forms from space.

• "Every day" technologies such as weather forecasting, remote sensing, GPS systems, satellite television, and some long distance communications systems critically rely on space infrastructure. Of sciences, astronomy and Earth sciences (via remote sensing) most notably benefit from space technology.

• Computers and telemetry were once leading edge technologies that might have been considered "space technology" because of their criticality to boosters and spacecraft. They existed prior to the Space Race of the Cold War (between the USSR and the USA.) but their development was vastly accelerated to meet the needs of the two major superpowers' space programs. While still used today in spacecraft and missiles, the more prosaic applications such as remote monitoring (via telemetry) of patients, water plants, highway conditions, etc. and the widespread use of computers far surpasses their space applications in quantity and variety of application.

• Space is such an alien environment that attempting to work in it requires new techniques and knowledge. New technologies originating with or accelerated by space-related endeavors are often subsequently exploited in other economic activities. This has been widely pointed to as beneficial by space advocates and enthusiasts favoring the investment of public funds in space activities and programs. Political opponents counter that it would be far cheaper to develop specific technologies directly if they are beneficial and scoff at this justification for public expenditures on space-related research.

Weather Forecasting

Analysis to Prognosis

Three important forecasting steps are:1) Assess the present state, called the analysis, 2) Predict a future state by running a computer model of weather changes3) Interpret the model results, called a prognostic chart, given forecasting experience

Viewing Data with AWIPS

Viewing weather images, overlays, and graphs in multiple windows is facilitated with the National Weather Service's Advanced Weather Interactive Processing System (AWIPS), which gathers data from the Automated Surface Observing System among other sources.

WSR-88D Doppler Radar

Weather Surveillance Radar - 1988 Doppler, also known as next generation radar (NEXRAD), detects severe weather size, movement, and intensity.

Data received by the NEXRAD unit are processed by algorithms to assist the forecaster in weather interpretation.

Meteogram Display

Predicted trends in several weather variables are plotted for a 60 hour period on a meteogram.

Patterns in variable response, such as rising pressure and a stop in precipitation, are readily observed.

Vertical Sounding Profile

Radiosonde instruments attached to pilot balloons are launched twice daily to profile weather variables with height.

These January 14, 1999 data show winds veering from easterly at the surface to southwesterly aloft that may change the freezing rain in the saturated lower atmosphere to non-freezing rain.

Probability Forecasts

Climate records, often 30 years of data, are used to generate probability forecasts for a given event.

In this case, most of Texas has a less than 5% chance of snow on December 25th, while northern Minnesota has had snow on that date for each of the past 30 years.

Weather Forecasting Methods

In this figure, the forecasting method is called weather types, which is a type of long range analogue forecast.

• Persistence - the future will be like the present

• Trend - the future will be like upwind weather

• Analogue - the future will be like weather that historically occurred when similar conditions were present

Weather Forecasting Methods

Weekly & Monthly Forecasts

Stationary weather systems often allow for trend based extended weather forecasts, while multiple runs of numerical weather models, known as ensemble forecasts, allow for 30 to 90 day outlooks.

Forecasting with Surface Charts

Many of the following figures analyze and predict weather for 6 U.S. cities.This simplified 6 AM Tuesday surface weather map is useful for short time interval predictions of fronts and associated weather.

Surface Chart Predictions

3-hour pressure tendencies plotted on isallobar maps help predict the movement of highs and lows and indicate how rapidly pressure systems are changing.

Lows tend to move toward the region of greatest pressure fall, while highs move toward the region of greatest rise.

The low from the previous map will likely move to the NE, while the high will move to the SE.

Upper Level ChartsUpper Level Charts

Upper level winds, particularly those at 5500 m, which is a common elevation for the 500 mb surface, often guide the path of surface pressure systems.

These upper level winds, however, travel at nearly twice the speed as the surface systems.

Here again, we see the low will head to the NE, while the high will head SE.

Figure 14.11Figure 14.11

Observed Movement of Fronts

Surface weather observations from 6 PM Tuesday and 6 AM Wednesday show how the fronts, pressure systems, and precipitation have moved as predicted.

Surface Weather for 6 AM Wednesday

Surface Weather for 4 PM Sunday

500 mb Chart for 4 PM Sunday

Surface Weather Map for 4 AM Monday

Remote Sensing Systems

Early Satellite Sensing

Spy satellites gave exquisite but very local views and were classifiedEven before satellites were launched, it was clear that color imaging was essentialBest images were from manned spacecraft Low latitude Limited coverage in space and time Almost all oblique

Gemini XII, 1968 (410 miles)

Early Satellite Sensing

Meteorological satellites gave hints of what might be possible Snow coverage Sea ice Glaciers Gross geological structures

Nimbus I image 1964

Landsat

Landsat 1 1972-1978Landsat 2 1975-1981 Landsat 3 1978-1983Landsat 4 1982-1993 Landsat 5 1984, still functioningLandsat 6 1993, failed to reach orbit Landsat 7 1999, still functioning, but with faulty scan line corrector (May 2003)Landsat Data Continuity Mission, scheduled for 2012

Two Key Features of Landsat

Orbits are sun synchronous: satellite crosses equator southbound on day side at about 10 AM local timeOrbits repeat ground track precisely every 14-18 days (Revisit period)A term to know: Nadir = point directly below (opposite of Zenith)

Early Landsat

Originally modeled on Nimbus weather satellite systemLandsat 1 observed in Green, Red and two IR bands with 80-m resolutionLandsat 3 had 30-m resolutionLandsat 3 added a fifth thermal IR band but it failedLandsat 4: 7 bandsLandsat 7: 15 m resolution panchromatic

Failed Experiment

President Jimmy Carter recommended private sector operation of Landsat, 1979Earth Observation Satellite Company (EOSAT), a partnership of Hughes Aircraft and RCA, was awarded ten year contract to operate Landsat, 1985EOSAT operated Landsats 4 and 5 and had exclusive rights to market Landsat data.EOSAT needed repeated bailoutsCongress passed Land Remote Sensing Policy Act (Public Law 102-555) and returned Landsat to public domain, 1992

Landsat 7 Bands1 0.45-0.52µm Blue-Green 30 m

2 0.52-0.60 µm Green 30 m

3 0.63-0.69 µm Red 30 m

4 0.76-0.90 µm Near IR 30 m

5 1.55-1.75 µm Mid-IR 30 m

6 10.40-12.50 µm Thermal IR 60 m

7 2.08-2.35 µm Mid-IR 30 m

0,52-0.90 µm Panchromatic 15 m

Uses of Landsat 7 Bands

1. Coastal water mapping, soil/vegetation discrimination, forest classification, man-made feature identification

2. Vegetation discrimination and health monitoring, man-made feature identification

3. Plant species identification, man-made feature identification

4. Soil moisture monitoring, vegetation monitoring, water body discrimination

5. Vegetation moisture content monitoring6. Surface temperature, vegetation stress monitoring,

soil moisture monitoring, cloud differentiation, volcanic monitoring

7. Mineral and rock discrimination, vegetation moisture content

False Color Images

Near IR (ETM+ band 4) Red Red (ETM+ band 3) Green Green (ETM+ band 2) Blue Colors on image are shifted one band toward blue compared to real scene

Making a False-Color Image

Landsat 7 Facts

Altitude: 705 kilometers Period: 98.9 minutesInclination: Sun-synchronous, 98.2 degreesEquatorial crossing: Southbound 10:00AM +/- 15 min.Repeat coverage interval: 16 days (233 orbits)Swath width: 185 kilometersOn-board data storage: ~375 Gb (solid state)

See SPOT. See SPOT See

Satellite Pour l'Observation de la TerreSun-synchronousAltitude: 832 kilometers, Inclination: 98.7Revisit period: 26 daysUses CCD’s and stare mode; no scanning

SPOT 5 Bands

Band (microns)

Colors Resolution

0.51 - 0.73 Panchromatic 2.5 & 5m

0.50 - 0.59 Green 10m

0.61 - 0.68 Red 10m

0.79 - 0.89 Near IR 10m

1.58 - 1.73 Mid IR 20m

SPOT Image of Kuwait City, 2004

IKONOS

1992 Land Remote Sensing Policy Act permitted private companies to enter the satellite imaging business. Lockheed MartinLaunched 20001 m resolution Bands: Blue, Green, Red, Near IRNow operated by GeoEye Inc., Dulles VA

Burj Khalifa by IKONOS

Terra

Part of NASA EOS (Earth Observation System)Partnership of U.S., Canada, JapanInstruments ASTER (Advanced Spaceborne Thermal Emission

and Reflection Radiometer) CERES (Clouds and Earth's Radiant Energy

System) MISR (Multiangle Imaging Spectroradiometer) MODIS (Moderate-Resolution Imaging

Spectroradiometer) MOPITT (Measurements of Pollution in the

Troposphere)

ASTER

U.S. – Japan joint missionThree Subsystems, each with own telescopesVNIR: Four visible and near-IR channels, 15-m resolutionSWIR: Six short wave IR channels, 30-m resolutionTIR: Five Thermal IR Channels, 90-m resolution IR sensors use Stirling Cycle coolers

MODIS

Resolutions 250, 500 and 1000 metersTen visible bands (250 and 500-m)Ten Near IR bands (500 and 1000 m)16 Medium and Thermal IR bands (1000 m)Bands are narrow and tailored to specific emissions and absorptions (ocean color, aerosols, ozone, water vapor, cloud temperature)

GPS

The Global Positioning System (GPS) is a space-based satellite navigation system that provides location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. The system provides critical capabilities to military, civil and commercial users around the world. It is maintained by the United States government and is freely accessible to anyone with a GPS receiver.The GPS project was developed in 1973 to overcome the limitations of previous navigation systems, integrating ideas from several predecessors, including a number of classified engineering design studies from the 1960s. GPS was created and realized by the U.S. Department of Defense (DoD) and was originally run with 24 satellites. It became fully operational in 1995. Bradford Parkinson, Roger L. Easton, and Ivan A. Getting are credited with inventing it.

Advances in technology and new demands on the existing system have now led to efforts to modernize the GPS system and implement the next generation of GPS III satellites and Next Generation Operational Control System (OCX). Announcements from Vice President Al Gore and the White House in 1998 initiated these changes. In 2000, the U.S. Congress authorized the modernization effort, GPS III.

In addition to GPS, other systems are in use or under development. The Russian Global Navigation Satellite System (GLONASS) was developed contemporaneously with GPS, but suffered from incomplete coverage of the globe until the mid-2000s.There are also the planned European Union Galileo positioning system, India's Indian Regional Navigational Satellite System and Chinese Compass navigation system.

Basic ConceptsA GPS receiver calculates its position by precisely timing the signals sent by GPS satellites high above the Earth. Each satellite continually transmits messages that include:the time the message was transmitted and,satellite position at time of message transmission.The receiver uses the messages it receives to determine the transit time of each message

and computes the distance to each satellite using the speed of light. Each of these distances and satellites' locations defines a sphere. The receiver is on the surface of each of these spheres when the distances and the satellites' locations are correct. These distances and satellites' locations are used to compute the location of the receiver using the navigation equations. This location is then displayed, perhaps with a moving map display or latitude and longitude; elevation or altitude information may be included, based on height above the geoid.Basic GPS measurements yield only a position, and neither speed nor direction. However,

most GPS units can automatically derive velocity and direction of movement from two or more position measurements. The disadvantage of this principle is that changes in speed or direction can only be computed with a delay, and that derived direction becomes inaccurate when the distance travelled between two position measurements drops below or near the random error of position measurement. GPS units can use measurements of the doppler shift of the signals received to compute velocity accurately. More advanced navigation systems use additional sensors like a compass or an inertial navigation system to complement GPS.

In typical GPS operation, four or more satellites must be visible to obtain an accurate result. Four sphere surfaces typically do not intersect. Because of this, it can be said with confidence that when the navigation equations are solved to find an intersection, this solution gives the position of the receiver along with the difference between the time kept by the receiver's on-board clock and the true time-of-day, thereby eliminating the need for a very large, expensive, and power hungry clock. The very accurately computed time is used only for display or not at all in many GPS applications, which use only the location. A number of applications for GPS do make use of this cheap and highly accurate timing. These include time transfer, traffic signal timing, and synchronization of cell phone base stations.Although four satellites are required for normal operation, fewer apply in special cases. If one variable is already known, a receiver can determine its position using only three satellites. For example, a ship or aircraft may have known elevation. Some GPS receivers may use additional clues or assumptions such as reusing the last known altitude, dead reckoning, inertial navigation, or including information from the vehicle computer, to give a (possibly degraded) position when fewer than four satellites are visible.

Structure

The current GPS consists of three major segments. These are the space segment (SS), a control segment (CS), and a user segment (US).The U.S. Air Force develops, maintains, and operates the space and control segments. GPS satellites broadcast signals from space, and each GPS receiver uses these signals to calculate its three-dimensional location (latitude, longitude, and altitude) and the current time.The space segment is composed of 24 to 32 satellites in medium Earth orbit and also includes the payload adapters to the boosters required to launch them into orbit. The control segment is composed of a master control station, an alternate master control station, and a host of dedicated and shared ground antennas and monitor stations. The user segment is composed of hundreds of thousands of U.S. and allied military users of the secure GPS Precise Positioning Service, and tens of millions of civil, commercial, and scientific users of the Standard Positioning Service

Applications

While originally a military project, GPS is considered a dual-use technology, meaning it has significant military and civilian applications.GPS has become a widely deployed and useful

tool for commerce, scientific uses, tracking, and surveillance. GPS's accurate time facilitates everyday activities such as banking, mobile phone operations, and even the control of power grids by allowing well synchronized hand-off switching.

Military

Attaching a GPS guidance kit to a dumb bomb, March 2003.As of 2009, military applications of GPS include:Navigation: GPS allows soldiers to find objectives, even in the dark or in unfamiliar territory, and to coordinate troop and supply movement. In the United States armed forces, commanders use the Commanders Digital Assistant and lower ranks use the Soldier Digital Assistant. Target tracking: Various military weapons systems use GPS to track potential ground and air targets before flagging them as hostile. These weapon systems pass target coordinates to precision-guided munitions to allow them to engage targets accurately. Military aircraft, particularly in air-to-ground roles, use GPS to find targets Missile and projectile guidance: GPS allows accurate targeting of various military weapons including ICBMs, cruise missiles, precision-guided munitions and Artillery projectiles. Embedded GPS receivers able to withstand accelerations of 12,000 g or about 118 km/s2 have been developed for use in 155 millimeters (6.1 in) howitzers.Search and Rescue: Downed pilots can be located faster if their position is known.Reconnaissance: Patrol movement can be managed more closely.GPS satellites carry a set of nuclear detonation detectors consisting of an optical sensor (Y-sensor), an X-ray sensor, a dosimeter, and an electromagnetic pulse (EMP) sensor (W-sensor), that form a major portion of the United States Nuclear Detonation Detection System. General William Shelton has stated that this feature may be dropped from future satellites in order to save money.

Restrictions on civilian use

The U.S. Government controls the export of some civilian receivers. All GPS receivers capable of functioning above 18 kilometers (11 mi) altitude and 515 meters per second (1,001 kn) or designed, modified for use with unmanned air vehicles like e.g. ballistic or cruise missile systems are classified as munitions (weapons) for which State Department export licenses are required. This rule applies even to otherwise purely civilian units that only receive the L1 frequency and the C/A (Coarse/Acquisition) code.Disabling operation above these limits exempts the receiver from

classification as a munitions. Vendor interpretations differ. The rule refers to operation at both the target altitude and speed, but some receivers stop operating even when stationary. This has caused problems with some amateur radio balloon launches that regularly reach 30 kilometers (19 mi).These limits only apply to units exported from (or which have

components exported from) the USA – there is a growing trade in various components, including GPS units, supplied by other countries, which are expressly sold as ITAR-free.

Satellite television

Satellite television is television programming delivered by the means of communications satellite and received by an outdoor antenna, usually a parabolic reflector generally referred to as a satellite dish, and as far as household usage is concerned, a satellite receiver either in the form of an external set-top box or a satellite tuner module built into a television set. Satellite television tuners are also available as a card or a USB peripheral to be attached to a personal computer. In many areas of the world satellite television provides a wide range of channels and services, often to areas that are not served by terrestrial or cable providers.Direct-broadcast satellite television comes to the general public in two distinct ways – analog and digital. This necessitates either having an analog satellite receiver or a digital satellite receiver. Analog satellite television is being replaced by digital satellite television and the latter is becoming available in a better quality known as high-definition television.

Categories of usage

There are three primary types of satellite television usage: reception direct by the viewer, reception by local television affiliates, or reception by head ends for distribution across terrestrial cable systems.Direct to the viewer reception includes direct broadcast satellite (or DBS) and television receive-only (or TVRO), both used for homes and businesses including hotels, among other properties.

Direct broadcast via satellite

Direct broadcast satellite, (DBS) also known as "Direct-To-Home" can either refer to the communications satellites themselves that deliver DBS service or the actual television service. DBS systems are commonly referred to as "mini-dish" systems. DBS uses the upper portion of the Ku band, as well as portions of the Ka band.

Modified DBS systems can also run on C-band satellites and have been used by some networks in the past to get around legislation by some countries against reception of Ku-band transmissions.

Most of the DBS systems use the DVB-S standard for transmission. With pay television services, the datastream is encrypted and requires proprietary reception equipment. While the underlying reception technology is similar, the pay television technology is proprietary, often consisting of a conditional-access module and smart card.This measure assures satellite television providers that only authorised, paying subscribers have access to pay television content but at the same time can allow free-to-air (FTA) channels to be viewed even by the people with standard equipment (DBS receivers without the conditional-access modules) available in the market.

Television receive-onlyThe term Television receive-only, or TVRO, arose during the early days of satellite television reception to differentiate it from commercial satellite television uplink and downlink operations (transmit and receive). This was before there was a DTH satellite television broadcast industry. Satellite television channels at that time were intended to be used by cable television networks rather than received by home viewers. Satellite television receiver systems were largely constructed by hobbyists and engineers. In 1978 Microcomm, a small company founded by radio amateur and microwave engineer H. Paul Shuch, introduced the first commercial home satellite television receiver. These early TVRO systems operated mainly on the C band frequencies and the dishes required were large; typically over 3 meters (10 ft) in diameter. Consequently TVRO is often referred to as "big dish" or "Big Ugly Dish" (BUD) satellite television.TVRO systems are designed to receive analog and digital satellite feeds of both television or audio from both C-band and Ku-band transponders on FSS-type satellites. The higher frequency Ku-band systems tend to be Direct To Home systems and can use a smaller dish antenna because of the higher power transmissions and greater antenna gain.TVRO systems tend to use larger rather than smaller satellite dish antennas, since it is more likely that the owner of a TVRO system would have a C-band-only setup rather than a Ku band-only setup. Additional receiver boxes allow for different types of digital satellite signal reception, such as DVB/MPEG-2 and 4DTV.The narrow beam width of a normal parabolic satellite antenna means it can only receive signals from a single satellite at a time. Simulsat or the Vertex-RSI TORUS, is a quasi-parabolic satellite earthstation antenna that is capable of receiving satellite transmissions from 35 or more C- and Ku-band satellites simultaneously.

Direct to Home television

Many satellite television customers in developed television markets get their programming through a direct broadcast satellite (DBS) provider. The provider selects programs and broadcasts them to subscribers as a set package. Basically, the provider’s goal is to bring dozens or even hundreds of channels to the customer's television in a form that approximates the competition from cable television. Unlike earlier programming, the provider’s broadcast is completely digital, which means it has high picture and stereo sound quality. Early satellite television services were broadcast in C-band radio, in the 3.7 GigaHertz (GHz) to 4.2 GHz frequency range. Digital broadcast satellite transmits programming in the Ku frequency range (10 GHz to 14 GHz).Programming sources are simply the channels that provide television programming for broadcast. The provider (the DTH platform) does not create original programming itself. The broadcast center is the central hub of the system. At the broadcast center, the television provider receives signals from various programming sources, compresses these signals using digital video compression (encryption if necessary), and sends a broadcast signal to the proper satellite.

Underground Space Technology

Tunnelling and Underground Space Technology is an international journalwhich publishes authoritative articles encompassing the development ofinnovative uses of underground space and the results of quality researchinto improved, more cost-effective techniques for the planning,geo-investigation, design, construction, operation and maintenance ofunderground and earth-sheltered structures.The journal provides an effectivevehicle for the improved worldwide exchange of information on developmentsin underground technology - and the experience gained from its use - and isstrongly committed to publishing papers on the interdisciplinary aspects ofcreating, planning, and regulating underground space. Towards this end,up-to-date reports of the International Tunnelling Association (ITA) workinggroups and important papers from major conferences sponsored by the ITA andother bodies are a regular feature of the journal