CU-Boulder Satellite Instrument to Provide New Details on Ozone

Just after 3 a.m. on July 10, University of Colorado at Boulder researcher John Gille expects to watch a new NASA satellite blast into orbit from the dark California coastline on a mission to study Earth's protective ozone layer, climate and air quality changes with unprecedented detail.

Gille, principal investigator on the satellite's High Resolution Dynamics Limb Sounder (HIRDLS) instrument, said he and his sleep-deprived colleagues will probably only get to watch the rocket for a few moments before it disappears into a thick deck of clouds that typically settles over the area this time of year.

The irony isn't lost on Gille, who's been at work on the instrument since 1988. "Writing about clouds in a meteorological journal, a scientist once said, 'There's no way to deal with these troublesome objects,' " he laughed.

Surface ozone pollution and air quality deterioration -- byproducts of agricultural burning, deforestation, urban activity and industry -- are increasing worldwide. Questions remain about the recovery of the protective ozone layer and the role of chemistry in climate change. HIRDLS and three other instruments on NASA's AURA satellite are designed to address these questions in detail.

HIRDLS is an international collaboration between scientists and engineers in the U.S. and Britain. Gille is HIRDLS U.S. principal investigator, and along with his Oxford University counterpart he is responsible for the overall success of the instrument, including design, testing, collection and use of data for scientific purposes.

At CU-Boulder, Gille is an adjoint professor in the Program in Atmospheric and Oceanic Sciences and senior research associate at the Center for Limb Atmospheric Sounding. "Limb" is the astronomical term for the edge of a planet and its atmosphere.

"Unlike the satellite images you see during TV weather forecasts, which are looking straight down at the Earth, our instrument is looking off toward the horizon," Gille said. "We look at the horizon from orbit, scanning up and down for a profile view."

The profile gives scientists insight into radiation, temperature and distribution of gases at different levels in the atmosphere. The data is then used to study the ozone layer, climate change and interaction between layers of the atmosphere.

HIRDLS will scan the mid- to upper-troposphere and the tropopause, the boundary region between the troposphere and the stratosphere. The troposphere extends upward from the Earth's surface to about 10 miles high at the equator and five miles high at the North and South poles. The stratosphere, which contains trace gases as well as the radiation-absorbing ozone layer, lies on top of the troposphere.

HIRDLS is expected to present a much clearer picture of whether the ozone layer is recovering, as well as the distribution of greenhouse gases that influence climate.

"HIRDLS has much finer horizontal resolution than we've ever had before," Gille said. "We can send commands to the satellite to zoom in and get readings with resolutions as fine as 30 to 60 miles, and a vertical resolution of 1,500 feet. Also, the HIRDLS detectors are up to 10 times more sensitive than similar instruments that have flown in the past."

The instrument is designed to last much longer in orbit than its predecessors, too. Thanks to an onboard mechanical refrigerator built by Ball Aerospace and Technologies Corp. of Boulder, scientists expect it will last longer than five years. It's hoped that longer-term trends can be predicted with the volume of data that will be collected.

The HIRDLS project began in 1988. Since that time, Gille and his research team at the university have led a collaborative effort to design and build the instrument with scientists and engineers at Oxford University in the United Kingdom, the National Center for Atmospheric Research in Boulder, the University of Washington and Lockheed Martin in Palo Alto, Calif.

Gille expects many of those who have worked on HIRDLS during the past 16 years to make the trip to Vandenburg Air Force Base, north of Santa Barbara, Calif., for the July 10 AURA launch at 3:01 a.m. Pacific Daylight Time.

For more information about the HIRDLS instrument visit http://www.eos.ucar.edu/hirdls/. For more information about CU-Boulder atmospheric research visit http://paos.colorado.edu/ and click on "Related Links

Earth satellite instrument

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man-made object launched into a temporary or permanent orbit around the Earth. Spacecraft of this type may be either manned or unmanned, the latter being the most common.

The idea of an artificial satellite in orbital flight was first suggested by Sir Isaac Newton in his book Philosophiae Naturalis Principia Mathematica (1687). He pointed out that a cannonball shot at a sufficient velocity from atop a mountain in a direction parallel to the horizon would go all the way around the Earth before falling. Although the object would tend to fall toward the Earth’s surface because of gravitational force, its momentum would cause it to descend along a curved path. Greater velocity would put it into a stable orbit, like that of the Moon, or direct it away from the Earth altogether. On Oct. 4, 1957, nearly three centuries after Newton had proposed his theory, the Soviet Union launched the first Earth satellite, Sputnik I. Sputnik circled the Earth every 96 minutes, and its simple radio signal was heard by scientists and radio operators across the world. The United States orbited its first satellite, Explorer 1, three months later (Jan. 31, 1958). Explorer, though much smaller than Sputnik, was instrumented to detect radiation and discovered the innermost of the two Van Allen radiation belts, a zone of electrically charged solar particles that surrounds the Earth.

Since these initial efforts, more than 5,000 Earth satellites have been orbited by at least 15 different nations. The satellites vary widely in size and design, ranging from a tiny sphere of several pounds equipped with only two radio transmitters to heavily instrumented space laboratories weighing many tons. They are equally diverse in function. Scientific satellites are chiefly used to collect data about the Earth’s surface and atmosphere and to make astronomical observations. Weather satellites transmit photographs of cloud patterns and measurements of other meteorological conditions that aid in weather forecasting, while communications satellites relay telephone calls, radio and television programs, and data communications between distant parts of the world. Navigation satellites enable the crews of oceangoing vessels and airplanes to determine the position of their craft in all kinds of weather. Some satellites have distinctly military applications, such as reconnaissance and surveillance.

Satellites can be placed in any number of different orbits. The particular path selected is largely determined by the function of the spacecraft. Most weather and reconnaissance satellites, for example, are fired into a polar orbit in which the Earth’s polar axis is a line on the orbital plane. Because the Earth rotates under polar-orbiting satellites, they pass over its entire surface within a given time period, providing full global coverage. Communications satellites, on the other hand, are generally placed into an equatorial orbit, which enables them to circle the most densely populated regions of the Earth from west to east. Moreover, communications satellites comprising a network or system are nearly always launched to a distance of 22,300 mi (35,890 km) above the Earth. At this altitude, the motion of a satellite becomes synchronized with the Earth’s rotation, causing the craft to remain fixed over a single location. If properly positioned, three communications satellites travelling in such a synchronous orbit can relay signals between stations around the world. See also spacecraft.

Blue Marble Next Generation

	Everyone knows that NASA studies space; fewer people know that NASA also studies Earth. Since the agency’s creation almost 50 years ago, NASA has been a world leader in space-based studies of our home planet. Our mission has always been to explore, to discover, and to understand the world in which we live from the unique vantage point of space, and to share our newly gained perspectives with the public. That spirit of sharing remains true today as NASA operates 18 of the most advanced Earth-observing satellites ever built, helping scientists make some of the most detailed observations ever made of our world.		Scroll to the bottom of the page for links to Blue Marble Next Generation imagery. Monthly global images shows changes over time on the Earth’s surface, with links to high-resolution images.
	In celebration of the deployment of its Earth Observing System, NASA is pleased to share the newest in its series of stunning Earth images, affectionately named the “Blue Marble.” This new Earth imagery enhances the Blue Marble legacy by providing a detailed look at an entire year in the life of our planet. In sharing these Blue Marble images, NASA hopes the public will join with the agency in its continuing exploration of our world from the unique perspective of space. To learn more about the development of NASA’s imagery of the Earth as a whole, read the History of the Blue Marble. Enhancements Blue Marble: Next Generation offers greater spatial detail of the surface and spans a longer data collection period than the original. The original Blue Marble was a composite of four months of MODIS observations with a spatial resolution (level of detail) of 1 square kilometer per pixel. Blue Marble: Next Generation offers a year’s worth of monthly composites at a spatial resolution of 500 meters. These monthly images reveal seasonal changes to the land surface: the green-up and dying-back of vegetation in temperate regions such as North America and Europe, dry and wet seasons in the tropics, and advancing and retreating Northern Hemisphere snow cover. From a computer processing standpoint, the major improvement is the development of a new technique for allowing the computer to automatically recognize and remove cloud-contaminated or otherwise bad data—a process that was previously done manually.		The Blue Marble: Next Generation is a series of images that show the color of the Earth’s surface for each month of 2004 at very high resolution (500 meters/pixel) at a global scale. This image shows South America from September 2004. (NASA image courtesy Reto Stöckli and Robert Simmon) High-resolution images: 1024 by 1024 screen (190 kB JPEG) 4096 by 4096 screen (1 MB JPEG) 4096 by 4096 print (12 MB PNG)
	Blue Marble: Next Generation improves the techniques for turning satellite data into digital images. Among the key improvements is greater detail in areas that usually appear very dark to the satellite (because a large amount of sunlight is being absorbed), for example in dense tropical forests. The ability to create a digital image that provides great detail in darker regions without “washing out” brighter regions, like glaciers, snow-covered areas, and deserts is one of the great challenges of visualizing satellite data. The new version also improves image clarity, and gives highly reflective land surfaces, such as salt flats, a more realistic appearance.		Monthly imagery shows seasonable variability, like the change in Alpine snow-cover from January to July. (NASA images by Reto Stöckli) High-resolution images: Alps, January 2004 (750 kB JPEG) Alps, July 2004 (650 kB JPEG)
	Limitations Those who intend to use the Blue Marble: Next Generation in their own publications or projects should be aware of areas that still require improvement. Areas of open water still show some “noise.” In tropical lowlands, cloud cover during the rainy season can be so extensive that obtaining a cloud-free view of every pixel of the area for a given month may not be possible. Deep oceans are not included in the source data; the creator of the Blue Marble uses a uniform blue color for deep ocean regions, and this value has not been completely blended with observations of shallow water in coastal areas. The lack of blending may, in some cases, make the transition between shallow coastal water and deep ocean appear unnatural. Finally, the data do not completely distinguish between snow and cloud cover in areas with short-term snow cover (less than three or four months). This problem may be resolved in the future through the use of a more sophisticated snow mask. Data Access Full-resolution, subsetted, and reduced-resolution files are available on the Blue Marble Next Generation collection on NASA’s Visible Earth. Monthly global images provides web-resolution copies of each of the monthly maps, along with links to 8km/pixel and 2km/pixel JPEGs, and full-resolution torrents. 500 meter/pixel images are available either via BitTorrent (see monthly global images page for links to torrent files) or from one of our mirror sites: Additional Download Sites: Arctic Region Supercomputing Center San Diego State University Sample 500 meter/pixel images. Animations: Seasonal Landcover Change over Western Asia in 2004 Seasonal Landcover Change over the Alps Seasonal Landcover Change over the Eastern United States Global Seasonal Landcover in 2004 Interactive viewers: Blue Marble Viewer EarthSLOT GeoFusion NASA JPL OnEarth NASA World Wind YaWah Credits Blue Marble: Next Generation was produced by Reto Stöckli, NASA Earth Observatory (NASA Goddard Space Flight Center). See The Blue Marble Next Generation—A true color Earth dataset including seasonal dynamics from MODIS (880 kB PDF) for acknowledgments. Anyone using or republishing Blue Marble: Next Generation please credit “NASA’s Earth Observatory.” References: Justice C.O., 1 Townshend J.R.G., Vermote E. F., Masuoka E., Wolfe R.E., El Saleous N., Roy D.P. and Morisette. J.T. , 2002. An overview of MODIS Land data processing and product status. Remote Sensing of Environment, 83, 1-2, 3-15. Los, S.O., Collatz, G.J., Sellers, P.J., Malmström, C.M., Pollack, N.H., DeFries, R.S., Bounoua, L., Parris, M.T., Tucker, C.J., and Dazlich, D.A. (2000) A global 9-year biophysical land-surface data set from NOAA AVHRR data. J Hydrometeor., 1, 183-199. Sellers, P.J., Los, S.O., Tucker, C.J., Justice, C.O., Dazlich, D.A., Collatz, G.J., and Randall, D.A. (1996) A revised land surface parameterization (SiB-2) for atmospheric GCMs. Part 2: The generation of global fields of terrestrial biophysical parameters from satellite data. Journal of Climate, 9, 706-737. Stöckli, R, and Vidale, P.L. (2004) European plant phenology and climate as seen in a 20 year AVHRR land-surface parameter dataset. Internat. J. Remote Sens., 25 (17), 3303-3330.		Improvements to the data-processing algorithms resulted in relatively noise-free images with few artifacts. Dry salt flats, such as the Etosha Pan in Namibia, rendered as water in the original Blue Marble, but are now accurately colored. (NASA images by Reto Stöckli.) High-resolution images: Etosha, January 2004 (240 kB JPEG) Etosha, July 2004 (220 kB

Moon

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Earth’s sole natural satellite and nearest large celestial body. Known since prehistoric times, it is the brightest object in the sky after the Sun. It is designated by the symbol ☽. Its name in English, like that of Earth, is of Germanic and Old English derivation.

The Moon’s desolate beauty has been a source of fascination and curiosity throughout history and has inspired a rich cultural and symbolic tradition. In past civilizations the Moon was regarded as a deity, its dominion dramatically manifested in its rhythmic control over the tides and the cycle of female fertility. Ancient lore and legend tell of the power of the Moon to instill spells with magic, to transform humans into beasts, and to send people’s behaviour swaying perilously between sanity and lunacy (from the Latin luna, “Moon”). Poets and composers were invoking the Moon’s romantic charms and its darker side, and writers of fiction were conducting their readers on speculative lunar journeys long before Apollo astronauts, in orbit above the Moon, sent back photographs of the reality that human eyes were witnessing for the first time.

Centuries of observation and scientific investigation have been centred on the nature and origin of the Moon. Early studies of the Moon’s motion and position allowed the prediction of tides and led to the development of calendars. The Moon was the first new world on which humans set foot; the information brought back from those expeditions, together with that collected by automated spacecraft and remote-sensing observations, has led to a knowledge of the Moon that surpasses that of any other cosmic body except Earth itself. Although many questions remain about its composition, structure, and history, it has become clear that the Moon holds keys to understanding the origin of Earth and the solar system. Moreover, given its nearness to Earth, its rich potential as a source of materials and energy, and its qualifications as a laboratory for planetary science and a place to learn how to live and work in space for extended times, the Moon remains a prime location for humankind’s first settlements beyond Earth orbit.

Properties of the Moon and the Earth-Moon system
	Moon	Earth	approximate ratio (Moon to Earth)
mean distance from Earth (orbital radius)	384,400 km	--	--
period of orbit around Earth (sidereal period of revolution)	27.3217 Earth days	--	--
inclination of equator to ecliptic plane (Earth’s orbital plane)	1.53°	23.45°	--
inclination of equator to body’s own orbital plane (obliquity to orbit)	6.68°	23.45°	--
inclination of orbit to Earth’s Equator	18.28°-28.58°	--	--
eccentricity of orbit around Earth	0.0549	--	--
recession rate from Earth	3.8 cm/year	--	--
rotation period	synchronous with orbital period	23.9345 hr	--
equatorial radius	1,738 km	6,378 km	1:4
surface area	37,900,000 km2	510,066,000 km2 (land area, 148,000,000 km2)	1:14
mass	0.0735 × 1024 kg	5.976 × 1024 kg	1:81
mean density	3.34 g/cm3	5.52 g/cm3	1:1.7
mean surface gravity	162 cm/sec2	980 cm/sec2	1:6
escape velocity	2.38 km/sec	11.2 km/sec	1:5
mean surface temperature	day, 380 K (224 °F, 107 °C); night, 120 K (-244 °F, -153 °C)	288 K (59 °F, 15 °C)	--
temperature extremes	396 K (253 °F, 123 °C) to 40 K (-388 °F, -233 °C)	331 K (136 °F, 58 °C) to 184 K (-128 °F, -89 °C)	--
surface pressure	3 × 10-15 bar	1 bar	1:300 trillion
atmospheric molecular density	day, 104 molecules/cm3; night, 2 × 105 molecules/cm3	2.5 × 1019 molecules/cm3 (at standard temperature and pressure)	about 1:100 trillion
average heat flow	29 mW/m2	63 mW/m2	1:2.2

Distinctive features

The Moon is a spherical rocky body, probably with a small metallic core, revolving around Earth in a slightly eccentric orbit at a mean distance of about 384,000 km (238,600 miles). Its equatorial radius is 1,738 km (1,080 miles), and its shape is slightly flattened in a such a way that it bulges a little in the direction of Earth. Its mass distribution is not uniform—the centre of mass is displaced about 2 km (1.2 miles) toward Earth relative to the centre of the lunar sphere, and it also has surface mass concentrations, called mascons for short, that cause the Moon’s gravitational field to increase over local areas. The Moon has no global magnetic field like that of Earth, but some of its surface rocks have remanent magnetism, which indicates one or more periods of magnetic activity in the past. The Moon presently has very slight seismic activity and little heat flow from the interior, indications that most internal activity ceased long ago.

Scientists now believe that more than four billion years ago the Moon was subject to violent heating—probably from its formation—which resulted in its differentiation, or chemical separation, into a less dense crust and a more dense underlying mantle. This was followed hundreds of millions of years later by a second episode of heating—this time from internal radioactivity—which resulted in volcanic outpourings of lava. The Moon’s mean density is 3.34 grams per cubic cm, close to that of Earth’s mantle. Because of the Moon’s small size and mass, its surface gravity is only about one-sixth of the planet’s; it retains so little atmosphere that the molecules of any gases present on the surface move without collision. In the absence of an atmospheric shield to protect the surface from bombardment, countless bodies ranging in size from asteroids to tiny particles have struck and cratered the Moon. This has formed a debris layer, or regolith, consisting of rock fragments of all sizes down to the finest dust. In the ancient past the largest impacts made great basins, some of which were later partly filled by the enormous lava floods. These great dark plains, called maria (singular mare [Latin: “sea”]), are clearly visible to the naked eye from Earth. The dark maria and the lighter highlands, whose unchanging patterns many people recognize as the “man in the moon,” constitute the two main kinds of lunar territory. The mascons are regions where particularly dense lavas rose up from the mantle and flooded into basins. Lunar mountains, located mostly along the rims of ancient basins, are tall but not steep or sharp-peaked, because all lunar landforms have been eroded by the unending rain of impacts. For additional orbital and physical data, see the table.

Satellite sensor maps global atmospheric ammonia emissions

7 July 2009
Using radiation measurements obtained by the MetOp satellite, scientists have produced the first complete map of global ammonia emissions – a pollutant of key environmental concern. The map, based on observations throughout 2008, shows inaccuracies in current ammonia inventories and identifies new hotspots.

Ammonia emissions contribute to a host of environmental problems, including soil acidification, reductions in biodiversity and the formation of atmospheric particulate matter, which has been linked to human health problems such as asthma. Yet despite its importance, many uncertainties remain about its global distribution.

Mapping ammonia is difficult, in part, because once emitted it only remains in the atmosphere for a short period. While in the atmosphere, however, it reacts with acid pollutants, such as nitric acid and sulfuric acid, to produce ammonium aerosol, which is believed to influence climate.

Lieven Clarisse and Pierre Coheur from the University of Bruxelles, Cathy Clerbaux from the French Scientific Research Centre (CNRS) and colleagues developed a methodology to be used with MetOp’s Infrared Atmospheric Sounding Interferometer (IASI) sensor that could isolate the signature of ammonia.

	Ammonia concentrations over Italy

By comparing the concentration map generated with IASI data obtained over a one-year period, which included more than a million measurements a day, with recent atmospheric models, the team was able to locate inconsistencies and identify ammonia hotspots across the globe.

Most of the hotspots appeared over agricultural regions in Europe, North America and Asia, as expected. However, the measurements taken from space over agricultural valleys, such as Italy’s Po Valley, Uzbekistan’s Fergana Valley and the US’s Snake River Valley in Idaho, were higher than the current inventories. The scientists also identified some sources in Central Asia that had not been included in current inventories.

Areas with biomass burning also had high ammonia emissions. For instance, increased ammonia concentrations were found over regions, such as Africa, Asia and South America, that had experienced a large number of fires.

Atmospheric ammonia is being increasingly recognised as a key pollutant that contributes to several environmental problems. In 1999 the UN Economic Commission for Europe (UNECE) set stringent reduction targets for ammonia to be obtained by 2010. However, reducing ammonia emissions has proved uncertain.

MetOp in orbit

Although more work is needed to detect low-level ammonia emissions from space, the techniques demonstrated by the team are very promising. With fine-tuning, Earth-observing satellites could provide the careful monitoring essential to ensuring these targets are met.

MetOp, launched in 2006, is the first of three meteorological satellites developed under a joint programme being carried out by ESA and the European Meteorological Satellite Organisation (EUMESAT). The IASI sensor was developed by CNES (the French space agency) in cooperation with EUMETSAT.

These new results, published online in Nature Geoscience in June, were obtained as part of a scientific project in response to a Research Announcement of Opportunity for MetOp, organised jointly by ESA and EUMETSAT. The support to scientific research by ongoing ESA programmes is important for developing and testing innovative methods with data from operational missions.

satellite

A satellite in polar orbit round the Earth. Satellites in polar orbit usually complete an orbit in two hours or less and as the Earth is rotating as they orbit, they cover a large part of the Earth's surface each day. Remote-sensing satellites, such as Landsat, are in polar orbit.

The British satellite Prospero continues to orbit the Earth every 100 minutes and will do so until 2040. With the correct equipment, the satellite's radio transmitter can still be heard broadcasting on 137.56 MHz.

Any small body that orbits a larger one. Natural satellites that orbit planets are called moons. The first artificial satellite, Sputnik 1, was launched into orbit around the Earth by the USSR in 1957. Artificial satellites can transmit data from one place on Earth to another, or from space to Earth. Satellite applications include science, communications, weather forecasting, and military use.

Space probes have been sent to natural satellites including the Earth's Moon, Mars's Deimos, and the moons of the giant planets Jupiter, Saturn, Uranus and Neptune.

At any time, there are several thousand artificial satellites orbiting the Earth, including active satellites, satellites that have ended their working lives, and discarded sections of rockets. The brightest artificial satellites can be seen by the naked eye. Artificial satellites eventually re-enter the Earth's atmosphere. Usually they burn up by friction, but sometimes debris falls to the Earth's surface, as with Skylab and Salyut 7.

Hundreds of millions of pieces of space junk, ranging from particles a millimetre across up to disabled satellites, are careering around the Earth. The US Space Command catalogues the larger items to make sure they are not mistaken for enemy missiles; currently about 10,000 items are listed.

Launch and mission

Soviet 40 copecks stamp, showing satellite's orbit.

The control system of the Sputnik Rocket was tuned to provide an orbit with the following parameters: perigee height - 223 km (139 mi), apogee height - 1,450 km (900 mi), orbital period - 101.5 min.^[39] A rocket trajectory with these parameters was calculated earlier by Georgi Grechko,^[40] after completing the calculations over several nights on the USSR Academy of Sciences's mainframe computer.^[20]

The Sputnik Rocket was launched at 19:28:34 UTC, on 4 October 1957, from Site No.1 at NIIP-5.^[41] Processing of the information, obtained from the "Tral" system showed^[20] that the side boosters separated 116.38 seconds into the flight and the second stage engine was shut-down 294.6 seconds into the flight.^[39] At this moment the second stage with PS-1 attached had a height of 223 km (139 mi) above Earth's surface, a velocity of 7,780 m/s (25,500 ft/s) and velocity vector inclination to the local horizon was 0 degrees 24 minutes. This motion resulted in an orbit with initial parameters: perigee height - 223 km, apogee height - 950 km (590 mi), initial orbital period - 96.2 minutes.^[39]

After 314.5 seconds PS-1 separated from the second stage^[39] and at the same moment at the small "Finnish house" of IP-1 station Junior Engineer-Lieutenant V.G.Borisov heard the "Beep-beep-beep" signals from the radio receiver R-250. Reception lasted for two minutes, while PS-1 was above the horizon. There were many people in the house, both military and civil, and they were probably the first to celebrate the event.^[20][42] After 325.44 seconds a corner reflector on the second stage was opened, that also allowed measurement of its orbit parameters - like the working "Tral" system did.^[29]

The designers, engineers and technicians who developed the rocket and satellite watched the launch from the range.^[43] After the launch they ran to the mobile radio station to listen to signals from the satellite.^[43] They waited about 90 minutes to ensure that the satellite had made one orbit and was transmitting, before Korolyov called Khrushchev.^[44] The downlink telemetry included data on temperatures inside and on the surface of the sphere.

On the first orbit the Telegraph Agency of the Soviet Union (TASS) transmitted: "As result of great, intense work of scientific institutes and design bureaus the first artificial Earth satellite has been built".^[45] The Sputnik 1 rocket booster (second stage of the rocket) also reached Earth orbit and was visible from the ground at night as a first magnitude object following the satellite. Korolyov had intentionally requested reflective panels placed on the booster in order to make it so visible.^[44] The satellite itself, a small but highly polished sphere, was barely visible at sixth magnitude, and thus more difficult to follow optically. Ahead of Sputnik 1 flew the third object - the payload fairing, 80 cm (31 in)-long cone, i.e. a little bit bigger than the satellite.