Lecture 5: Orbit focus on nearly circular orbits which are quite common and also easy to treat mathematically

Number of Objects in Space: 1957 to present http://www.youtube.com/watch?v=6Qf6VIvLGZk&feature=related

read King et al. Appendix

The Afternoon Constellation “A-Train” The Afternoon constellation consists of 7 U.S. and international Earth Science satellites that fly within approximately 30 minutes of each other to enable coordinated science The joint measurements provide an unprecedented sensor system for Earth observations 4

Atmospheric Remote Sensing Sensors, Satellite Platforms, and Orbits Satellite orbits and platforms Low Earth orbit Sunsynchronous and repeat coverage Precessing Geosynchronous orbit Sensor scanning modes Whiskbroom and pushbroom scanners Active and passive microwave radiometers Next lecture 5

Satellite Orbits At what location is the satellite looking? When is the satellite looking at a given location? How often is the satellite looking at a given location? At what angle is the satellite viewing a given location?

Altitude classifications Low Earth orbit (LEO): Geocentric orbits ranging in altitude from 0–2000 km (0–1240 miles) Medium Earth orbit (MEO): Geocentric orbits ranging in altitude from 2000 km (1240 miles) to just below geosynchronous orbit at 35786 km (22240 miles). Also known as an intermediate circular orbit. High Earth orbit (HEO): Geocentric orbits above the altitude of geosynchronous orbit 35786 km (22240 miles).

Satellites in Geosynchronous Orbits are used as Relay Satellites for LEO Spacecraft Imaging System (e.g., Landsat) LEO Ground station Communication relay system GEO Communication relay system (e.g., TDRSS)

Key Parameters for Orbit the satellite’s height, eccentricity, and inclination determine the satellite’s path and what view it will have of Earth.

Kepler’s laws Satellites follow an elliptical orbit with the Earth as one focus Perigee Apogee Foci 3rd law (law of harmonics): The square of a planet's orbital period is proportional to its mean distance from the cube of semi-major axis of its orbit. The mathematical way to describe Kepler's 3rd law is: T2 ~a3

Kepler’s Laws 1. All satellites travel in ellipse paths with the Earth at one focus. 2. The radius vector from the Earth to a satellite sweeps out equal areas in equal times. 3. see last page

Physics for Satellite Orbit

42 T2= r3 GM Centripetal Force, Gravity When a body moving in a circle, from Newton's 2nd law there must be a force acting on it to cause the acceleration. This force will also be directed toward the centre and is called the centripetal force. F1 = mac = mv2/r = mrω2 Where m is the mass of the body and v is the speed in the circular path of radius r Newton's 2nd law F2 = mag ag= GM/r2 ω=2π/T T2= r3 42 GM r: distance from satellite to the center of earth M: mass of the Earth

Period of orbit Period of orbit T2= r3 42 GMe Radius of the orbit Gravitational constant Mass of the Earth Valid only for circular orbits (but a good approximation for most satellites) Radius is measured from the center of the Earth (satellite altitude+Earth’s radius) Accurate periods of elliptical orbits can be determined with Kepler’s Equation

Definition of Orbital Period of a Satellite The orbital period of a satellite around a planet is given by where T0 = orbital period (sec) Rp = planet radius (6380 km for Earth) H¢ = orbit altitude above planet’s surface (km) G = acceleration due to gravity (0.00981 km s-2 for Earth) Class activity: H=705 Km, T=?

Eccentricity Eccentricity refers to the shape of the orbit. A satellite with a low eccentricity orbit moves in a near circle around the Earth. An eccentric orbit is elliptical, with the satellite’s distance from Earth changing depending on where it is in its orbit.

For fun Molniya (satellite) http://www.youtube.com/watch?v=x3dtoq9Xl3s&feature=fvwrel Molniya (Russian: Молния, meaning "lightning") was a military communications satellite system used by the Soviet Union. The satellites were placed into highly eccentric elliptical orbits known as Molniya orbits, characterised by an inclination of +63.4 degrees and a period of around 12 hours. Such orbits allowed them to remain visible to sites in polar regions for extended periods, unlike satellites in geosynchronous orbits. The Molniya program was authorized by a government decree in late 1960. After some initial failures in 1964, the first operational satellite, Molniya 1-01, was successfully launched on April 23, 1965.

Orbital inclination Inclination is the angle of the orbit in relation to Earth’s equator. A satellite that orbits directly above the equator has zero inclination. If a satellite orbits from the north pole (geographic, not magnetic) to the south pole, its inclination is 90 degrees.

Inclination Angle the inclination angle is zero if the the orbital plane coincides with the equatorial plane and if the satellite rotates in the same direction as the Earth. If the two planes coincides but the satellite rotates opposite to as the Earth, the inclination angle is 180 degree. Prograde orbits are those with inclination angle less than 90 degree; retrograde orbits are those with it greater than 90 degree.

Types of orbits (1) Sunsynchronous orbits: An orbit in which the satellite passes every location at the same time each day Noon satellites: pass over near noon and midnight Morning satellites: pass over near dawn and dusk Often referred to as “polar orbiters” because of the high latitudes they cross Usually orbit within several hundred to a few thousand km from Earth

Types of orbits (2) Geostationary (geosynchronous) orbits: An orbit which places the satellite above the same location at all times Must be orbiting approximately 36,000 km above the Earth Satellite can only “see” one hemisphere

Geosynchronous Orbits http://www.youtube.com/watch?v=chQiZhARU9M&feature=related

How Low Earth Orbiting Satellite Systems Work http://www.youtube.com/watch?v=m2WrY1GdQ74&NR=1&feature=endscreen

Sunsynchronous (Near Polar) Video Sun-Synchronous Orbit at 800km Terra orbit – http://www.met.sjsu.edu/~jin/video/TerraOrbit.mpg Earth Observing Fleet movie http://www.met.sjsu.edu/~jin/video/Earth%20Observing%20Fleet.mov http://science-edu.larc.nasa.gov/SCOOL/orbits.html

Low Earth Orbit Concepts Descending node Ascending node Perigee Ground track Orbit Inclination angle Equator Orbit South Pole Apogee

Sun-Synchronous Orbit of Terra

Spacing Between Adjacent Landsat 5 or 7 Orbit Tracks at the Equator

Timing of Adjacent Landsat 5 or 7 Coverage Tracks Adjacent swaths are imaged 7 days apart

Tropical Rainfall Measuring Mission Orbit (Precessing) A precessing low-inclination (35°), low-altitude (350 km) orbit to achieve high spatial resolution and capture the diurnal variation of tropical rainfall Raised to 402 km in August 2001 Before we can justify flying a fleet of satellites to observe rainfall from space, we must first demonstrate that we can achieve high-quality rainfall measurements from space. TRMM was meant to provide that proof-of-concept demonstration using one satellite. The necessary compromise was reduced global coverage and temporal sampling. The issue of limited sampling had, no doubt, been a factor in promoting TRMM as a climate observation program, but that was before using these observations in data assimilation. We now know that we can derive tremendous from space-based rainfall observations even with limited sampling, a point that I will return to later.

TRMM Coverage 1 day coverage 2 day coverage Before we can justify flying a fleet of satellites to observe rainfall from space, we must first demonstrate that we can achieve high-quality rainfall measurements from space. TRMM was meant to provide that proof-of-concept demonstration using one satellite. The necessary compromise was reduced global coverage and temporal sampling. The issue of limited sampling had, no doubt, been a factor in promoting TRMM as a climate observation program, but that was before using these observations in data assimilation. We now know that we can derive tremendous from space-based rainfall observations even with limited sampling, a point that I will return to later.

Orbital Characteristics of Selected Missions Low Earth Orbit & Precessing Missions

The Afternoon Constellation “A-Train” The Afternoon constellation consists of 7 U.S. and international Earth Science satellites that fly within approximately 30 minutes of each other to enable coordinated science The joint measurements provide an unprecedented sensor system for Earth observations 35

Story shared by M. King “This is an engineering feat.  All satellites ARE at the same altitude (or were).  PARASOL is old and has left the A-Train (altitude) to conserve fuel.  Not only are they in the same orbit and close together, they are not all controlled by NASA.  CNES controlled PARASOL and the Air Force CloudSat, as I recall, and the Japanese no doubt control their own GCOM-W.  Much coordination for orbit and inclination adjust maneuvers is required, and in some cases we know of space debris but can't tell our foreign partners (due to ITAR), and so we had to tell the French once not to do a maneuver when they intended because they may very well get hit by space debris, but we couldn't tell them what it was or how we knew.”

Sunsynchronous image (AVHRR) Operators NOAA (National Oceanic and Atmospheric Administration) Date of Launch NOAA-N (NOAA-18): 20 May 2005 NOAA-19: 6 Feb 2009 Status Operational Orbit Height 833±19 km or 870±19 km Orbit Type Sun-synchronous circular, PM orbit Repeat Cycle daily Resolution 1 km Swath Width 2900 km

Geostationary Image (GOES-8) 35,800 km (22,300 miles) above the Earth GOES satellites orbit the equatorial plane of the Earth at a speed matching the Earth's rotation. This allows them to hover continuously over one position on the surface The geosynchronous plane is about 35,800 km (22,300 miles) above the Earth, high enough to allow the satellites a full-disc view of the Earth. Because they stay above a fixed spot on the surface, they provide a constant vigil for the atmospheric "triggers" for severe weather conditions such as tornadoes, flash floods, hail storms, and hurricanes.

Geostationary satellites GMS (Japan) Geostationary Meteorological Satellite Located over 140ºE longitude Similar to older GOES satellites Insat (India) Located over 74ºE longitude Insat 1B similar to GOES-8/9 Meteosat (European Union) Located over 0º longitude FY 2 and FY 4 (China)

Geosynchronous Meteorological Satellites WMO Member States

Geostationary satellites GOES 4-7 (USA) Geostationary Operational Environmental Satellite Spin stabilized... pointing toward Earth 5% of the time Rotation rate of 100 rpm, 18.21 minutes are required to complete one full scan VAS (VISSR Atmospheric Sounder) Visible/Infrared Imaging Spin Scan Radiometer

Geostationary satellites GOES-8/(9)/10/11/12 (USA) GHIS (GOES High Resolution Interferometer Sounder) Sounder 2-3X more accurate 5 Visible/IR channels 18 IR sounder bands (channels) 3-axis stabilized... always pointing toward Earth 75ºW-GOES 12; 135ºW-GOES 11

44

GOES-8/10 imager 45

GOES-8/10 imager 46

GOES-east (fyi) ECCENTRICITY: 0.000291 INCLINATION (DEG): 0.081813 ASCENDING NODE (DEG): 160.126382 PERIGEE (DEG): 149.175889 APOGEE HT (KM): 35800.56611 PERIGEE HT (KM): 35776.06619 LONGITUDE (DEG WEST): 74.599 LONGITUDE DRIFT RATE (DEG/DAY): 0.006000 EAST TOTAL MASS (KG): 1953.091 THE FOLLOWING ELEMENTS AS PROVIDED BY SOCC NAVIGATION.

What’s Next GOES-13 launched in 2006 GOES-O launched on 20 July 2008 GOES-P launched on 30 May 2009 GOES-Q has no spacecraft manufacturer or launch date (Cancelled) GOES-R series of spacecraft is in the formulation phase.

GOES-R Scheduled for 2014

Clouds Pollution Haze Severe storms Channel 1: 0.52-0.72 m (Visible)

Nighttime fog Nighttime SSTs Liquid vs. ice clouds Fires and volcanoes Channel 2: 3.78-4.03m (Shortwave infrared)

Standard water vapor Mid-level moisture Mid-level motion Channel 3: 6.47-7.02 m (Upper-level water vapor)

Standard IR channel Winds Severe storms Heavy rainfall Channel 4: 10.2-11.2 m (Longwave infrared)

Low-level moisture SSTs Volcanic dust or ash Channel 5: 11.5-12.5 m (Infrared/water vapor)

Sounder IR bands 2, 3, 4 and 5 (temperature)

Sounder IR bands 8, 10, 11 and 12 (water vapor)

Why different Orbits? "The spatial and temporal variability of the phenomenon to be studied will determine the observing strategy to be employed, and this will have an influence on the choice of operational parameters in the case of an airborne observation or on the orbital parameters in the case of a satellite-borne sensor". Above considerations will also place limits on the type of sensor to be employed.

FYI The following section is just FYI

GOES-8/10 sounder

GOES-8/10 sounder

Non-Photographic Sensor Systems 1800 Discovery of the IR spectral region by Sir William Herschel. 1879 Use of the bolometer by Langley to make temperature measurements of electrical objects. 1889 Hertz demonstrated reflection of radio waves from solid objects. 1916 Aircraft tracked in flight by Hoffman using thermopiles to detect heat effects. 1930 Both British and Germans work on systems to locate airplanes from their thermal patterns at night. 1940 Development of incoherent radar systems by the British and United States to detect and track aircraft and ships during W.W.II. 1950's Extensive studies of IR systems at University of Michigan and elsewhere. 1951 First concepts of a moving coherent radar system. 1953 Flight of an X-band coherent radar. 1954 Formulation of synthetic aperture concept (SAR) in radar. 1950's Research development of SLAR and SAR systems by Motorola, Philco, Goodyear, Raytheon, and others. 1956 Kozyrev originated Frauenhofer Line Discrimination concept. 1960's Development of various detectors which allowed building of imaging and non-imaging radiometers, scanners, spectrometers and polarimeters. 1968 Description of UV nitrogen gas laser system to simulate luminescence.

Sunsynchronous satellites TIROS (renamed NOAA) (USA) Advanced Very High Resolution Radiometer 1.1km resolution (LAC) or 4km (GAC) Channel 3A (1.6 m) added to new AVHRR/3 sensor in spring 1996

AVHRR thermal IR imagery of Gulf Stream

AVHRR multi-channel SSTs

AVHRR Normalized Difference Vegetation Index TIROS AVHRR Normalized Difference Vegetation Index

Sunsynchronous satellites: TIROS/NOAA TIROS Operational Vertical Sounder (TOVS) October 78 to present Three units to TOVS: MSU, HIRS, SSU (Stratospheric Sounding Unit) High Resolution Infrared Radiation Sounder (HIRS/2 & /3 Vertical temperature profiles to 40km 20 infrared bands Microwave Sounding Unit (MMU) Vertical temperature profile to 20km 4 microwave channels Complements HIRS when clouds are present

MSU mid-troposphere temperatures

MSU mid-troposphere vorticity

Sunsynchronous satellites: TIROS/NOAA Advanced Microwave Sounding Unit (3 units) AMSU-A1, AMSU-A2, AMSU-B Replace MSU and SSU

POES Satellite Soundings 24 Hour Coverage - 2 Satellites Total Precipitable Water http://poes.nesdis.noaa.gov/posse/

POES Satellite Soundings Coverage in Polar Regions Gray: Clear Areas White/Blue: Clouds Soundings Available for Both Clear and Cloudy Conditions

POES Satellite Soundings Individual Temperature/Moisture Profile

Sunsynchronous satellites Defense Meteorological Satellite Program (DMSP) (USA) Operational Linescan System (OLS) Visible imagery (0.55km resolution) Visible and thermal IR channels

DMSP OLS image of Hurricane Emily

DMSP OLS image of city lights

Sunsynchronous satellites: DMSP Special Sensor Microwave/Imager 19, 22, 37 and 85 GHz channels Uses include: snow cover, sea ice, precipitation rate, oceanic wind speed, water vapor, soil moisture Similar sensors: SMMR and ESMR Microwave temperature sounder (SSM/T) Microwave water vapor profiler (SSM/T2)

DMSP SSM/I precipitation rates during the Blizzard of ‘93

NPOESS National Polar Orbiting Operational Environmental Satellite System Will converge NOAA, DoD and NASA missions in a next generation instrument. Follow on to NOAA series of satellite (AVHRR) and DoD DMSP series Continues NASA’s EOS Terra and Aqua missions Launch 2009 with missions to 2018???

NPOESS instruments 1330 1730 2130 NPP    1330   1730   2130   NPP  Visible/Infrared Imager/Radiometer Suite (VIIRS) X Conical Microwave Imager/Sounder (CMIS) Crosstrack Infrared Sounder (CrIS) Advanced Technology Microwave Sounder (ATMS) Space Environment Sensor Suite (SESS) Ozone Mapping and Profiler Suite (OMPS) Advance Data Collection System (ADCS) Search and Rescue Satellite Aided Tracking (SARSAT) Total Solar Irradiance Sensor (TSIS) Earth Radiation Budget Sensor (ERBS) RADAR Altimeter (ALT) Aerosol Polarimeter Sensor (APS) Survivability Sensor (SS)

NPOESS Preparatory Mission NPP is a bridge between the EOS program and NPOESS for the development of the following sensors: Advanced Technology Microwave Sounder (ATMS) Cross-track Infrared Sounder (CrIS) Ozone Mapping and Profiler Suite (OMPS) Visible/Infrared Imager Radiometer Suite (VIIRS) Its mission is to demonstrate advanced technology and giving continuing observations about global change after EOS-PM (Terra) and EOS-AM (Aqua). Launch late ??

How many satellite in space? http://www.youtube.com/watch?v=cfSaztUiw5s&feature=related How To Understand Satellites In Its Orbit   http://www.youtube.com/watch?v=uEe5GMzcupw&feature=related