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114-418: The metric is popular in industry because of its accuracy. It has a high correlation with the true state of vegetation on the ground. The index is easy to interpret: NDVI will be a value between -1 and 1. An area with nothing growing in it will have an NDVI of zero. NDVI will increase in proportion to vegetation growth. An area with dense, healthy vegetation will have an NDVI of one. NDVI values less than 0 suggest

228-415: A barometric switch, activated if the pressure inside the satellite fell below 130 kPa, which would have indicated failure of the pressure vessel or puncture by a meteor, and would have changed the duration of radio signal impulse. While attached to the rocket, Sputnik 1 was protected by a cone-shaped payload fairing , with a height of 80 cm (31.5 in). The fairing separated from both Sputnik and

342-474: A dense vegetation canopy will tend to positive values (say 0.3 to 0.8) while clouds and snow fields will be characterized by negative values of this index. Other targets on Earth visible from space include: In addition to the simplicity of the algorithm and its capacity to broadly distinguish vegetated areas from other surface types, the NDVI also has the advantage of compressing the size of the data to be manipulated by

456-596: A dominant issue in the 1960 presidential campaign . The Communist Party newspaper Pravda only printed a few paragraphs about Sputnik 1 on 4 October. Sputnik also inspired a generation of engineers and scientists. Harrison Storms, the North American designer who was responsible for the X-15 rocket plane, and went on to head the effort to design the Apollo command and service module and Saturn V launch vehicle's second stage,

570-406: A factor 2 (or more), since it replaces the two spectral bands by a single new field (eventually coded on 8 bits instead of the 10 or more bits of the original data). The NDVI has been widely used in applications for which it was not originally designed. Using the NDVI for quantitative assessments (as opposed to qualitative surveys as indicated above) raises a number of issues that may seriously limit

684-515: A known distance. Tracking of the booster during launch had to be accomplished through purely passive means, such as visual coverage and radar detection. R-7 test launches demonstrated that the tracking cameras were only good up to an altitude of 200 km (120 mi), but radar could track it for almost 500 km (310 mi). Outside the Soviet Union, the satellite was tracked by amateur radio operators in many countries. The booster rocket

798-608: A lack of dry land. An ocean will yield an NDVI of -1 The exploration of outer space started in earnest with the launch of Sputnik 1 by the Soviet Union on 4 October 1957. This was the first man-made satellite orbiting the Earth . Subsequent successful launches, both in the Soviet Union (e.g., the Sputnik and Cosmos programs), and in the U.S. (e.g., the Explorer program ), quickly led to

912-617: A leading Soviet physicist, announced that they too would launch an artificial satellite. On 8 August, the Politburo of the Communist Party of the Soviet Union approved the proposal to create an artificial satellite. On 30 August, Vasily Ryabikov—the head of the State Commission on the R-7 rocket test launches—held a meeting where Korolev presented calculation data for a spaceflight trajectory to

1026-435: A means to adjust for or “normalize” the effects of the solar zenith angle. Originally, they called this ratio the “Vegetation Index” (and another variant, the square-root transformation of the difference-sum ratio, the “Transformed Vegetation Index”); but as several other remote sensing researchers were identifying the simple red/infrared ratio and other spectral ratios as the “vegetation index,” they eventually began to identify

1140-434: A new generation of algorithms were proposed to estimate directly the biogeophysical variables of interest (e.g., the fraction of absorbed photosynthetically active radiation , FAPAR), taking advantage of the enhanced performance and characteristics of modern sensors (in particular their multispectral and multiangular capabilities) to take all the perturbing factors into account. In spite of many possible perturbing factors upon

1254-556: A newly-installed computer at the Academy of Sciences . A special reconnaissance commission selected Tyuratam for the construction of a rocket proving ground , the 5th Tyuratam range, usually referred to as "NIIP-5", or "GIK-5" in the post-Soviet time. The selection was approved on 12 February 1955 by the Council of Ministers of the USSR, but the site would not be completed until 1958. Actual work on

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1368-455: A practical disadvantage as compared to NDVI. Also in this regard, note that the VIS term in the numerator of NDVI only scales the result, thereby creating negative values. NDVI is functionally and linearly equivalent to the ratio NIR / (NIR+VIS), which ranges from 0 to 1 and is thus never negative nor limitless in range. But the most important concept in the understanding of the NDVI algebraic formula

1482-461: A redesign to completely fulfill its military purpose. The rocket, however, was deemed suitable for satellite launches, and Korolev was able to convince the State Commission to allow the use of the next R-7 to launch PS-1, allowing the delay in the rocket's military exploitation to launch the PS-1 and PS-2 satellites. On 22 September a modified R-7 rocket, named Sputnik and indexed as 8K71PS, arrived at

1596-583: A report by Mikhail Tikhonravov , with an overview of similar projects abroad. Tikhonravov had emphasized that the launch of an orbital satellite was an inevitable stage in the development of rocket technology. On 29 July 1955, U.S. President Dwight D. Eisenhower announced through his press secretary that, during the International Geophysical Year (IGY), the United States would launch an artificial satellite. Four days later, Leonid Sedov ,

1710-509: A system of ground stations was to be developed to collect data transmitted by the satellite, observe the satellite's orbit, and transmit commands to the satellite. Because of the limited time frame, observations were planned for only 7 to 10 days and orbit calculations were not expected to be extremely accurate. By the end of 1956, it became clear that the complexity of the ambitious design meant that 'Object D' could not be launched in time because of difficulties creating scientific instruments and

1824-448: A trajectory measurement system called "Tral", developed by OKB MEI (Moscow Energy Institute), by which they received and monitored data from transponders mounted on the R-7 rocket's core stage. The data were useful even after the satellite's separation from the second stage of the rocket; Sputnik's location was calculated from data on the location of the second stage, which followed Sputnik at

1938-428: A velocity of 7,780 m/s (25,500 ft/s), and a velocity vector inclination to the local horizon of 0 degrees 24 minutes. This resulted in an initial elliptical orbit of 223 km (139 mi) by 950 km (590 mi), with an apogee approximately 500 km (310 mi) lower than intended, and an inclination of 65.10° and a period of 96.20 minutes. Several engines did not fire on time, almost aborting

2052-412: Is Russian for satellite when interpreted in an astronomical context; its other meanings are spouse or traveling companion . Tracking and studying Sputnik 1 from Earth provided scientists with valuable information. The density of the upper atmosphere could be deduced from its drag on the orbit, and the propagation of its radio signals gave data about the ionosphere . Sputnik 1 was launched during

2166-526: Is a special function called the polylogarithm . By definition, the exergy obtained by the receiving body is always lower than the energy radiated by the emitting blackbody, as a consequence of the entropy content in radiation. Thus, as a consequence of the entropy content, not all the radiation reaching the Earth's surface is "useful" to produce work. Therefore, the efficiency of a process involving radiation should be measured against its exergy, not its energy. Using

2280-409: Is agriculture drones from PrecisionHawk and Sentera, which allow agriculturalists to capture and process NDVI data within one day, a change from the traditional NDVI uses and their long lag times. Much of the research done currently has proved that the NDVI images can even be obtained using the normal digital RGB cameras by some modifications in order to obtain the results similar to those obtained from

2394-444: Is calculated from these individual measurements as follows: where Red and NIR stand for the spectral reflectance measurements acquired in the red (visible) and near-infrared regions, respectively. These spectral reflectances are themselves ratios of the reflected radiation to the incoming radiation in each spectral band individually, hence they take on values between 0 and 1. By design, the NDVI itself thus varies between -1 and +1. NDVI

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2508-516: Is determined as: about 8.3% lower than the value considered until now, as a direct consequence of the fact that the organisms which are using solar radiation are also emitting radiation as a consequence of their own temperature. Therefore, the conversion factor of the organism will be different depending on its temperature, and the exergy concept is more suitable than the energy one. Researchers at Utah State University compared measurements for PPF and YPF using different types of equipment. They measured

2622-411: Is directly related to the photosynthetic capacity and hence energy absorption of plant canopies. Although the index can take negative values, even in densely populated urban areas the NDVI usually has a (small) positive value. Negative values are more likely to be observed in the atmosphere and some specific materials . It can be seen from its mathematical definition that the NDVI of an area containing

2736-453: Is equivalent to 3.8 × 4.56 = 17.3 μmol/s. For a black-body light source at 5800 K, such as the sun is approximately, a fraction 0.368 of its total emitted radiation is emitted as PAR. For artificial light sources, that usually do not have a black-body spectrum, these conversion factors are only approximate. The quantities in the table are calculated as where B ( λ , T ) {\displaystyle B(\lambda ,T)}

2850-443: Is functionally, but not linearly, equivalent to the simple infrared/red ratio (NIR/VIS). The advantage of NDVI over a simple infrared/red ratio is therefore generally limited to any possible linearity of its functional relationship with vegetation properties (e.g. biomass). The simple ratio (unlike NDVI) is always positive, which may have practical advantages, but it also has a mathematically infinite range (0 to infinity), which can be

2964-528: Is nonstandard and is no longer used. There are two common measures of photosynthetically active radiation: photosynthetic photon flux (PPF) and yield photon flux (YPF). PPF values all photons from 400 to 700 nm equally, while YPF weights photons in the range from 360 to 760 nm based on a plant's photosynthetic response. PAR as described with PPF does not distinguish between different wavelengths between 400 and 700 nm, and assumes that wavelengths outside this range have zero photosynthetic action. If

3078-416: Is relevant in energy-balance considerations for photosynthetic organisms . However, photosynthesis is a quantum process and the chemical reactions of photosynthesis are more dependent on the number of photons than the energy contained in the photons. Therefore, plant biologists often quantify PAR using the number of photons in the 400-700 nm range received by a surface for a specified amount of time, or

3192-401: Is that, despite its name, it is a transformation of a spectral ratio (NIR/VIS), and it has no functional relationship to a spectral difference (NIR-VIS). In general, if there is much more reflected radiation in near-infrared wavelengths than in visible wavelengths, then the vegetation in that pixel is likely to be dense and may contain some type of forest. Subsequent work has shown that the NDVI

3306-481: Is the black-body spectrum according to Planck's law , y {\displaystyle y} is the standard luminosity function , λ 1 , λ 2 {\displaystyle \lambda _{1},\lambda _{2}} represent the wavelength range (400–700 nm) of PAR, and N A {\displaystyle N_{\text{A}}} is the Avogadro constant . Besides

3420-486: Is the general term for the artificial satellites of any country and the natural satellites of any planet. The incorrect attribution of 'Sputnik' as a proper name can be traced back to an article released by The New York Times on October 6, 1957, titled "Soviet 'Sputnik' Means A Traveler's Traveler". In the referenced article, the term 'Sputnik' was portrayed as bearing a poetic connotation arising from its linguistic origins. This connotation incorrectly indicated that it

3534-524: The International Geophysical Year from Site No.1/5 , at the 5th Tyuratam range, in Kazakh SSR (now known as the Baikonur Cosmodrome ). The satellite traveled at a peak speed of about 8 km/s (18,000 mph), taking 96.20 minutes to complete each orbit. It transmitted on 20.005 and 40.002 MHz, which were monitored by radio operators throughout the world. The signals continued for 22 days until

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3648-653: The National Aeronautics and Space Act ), as well as increased U.S. government spending on scientific research and education through the National Defense Education Act . Sputnik also contributed directly to a new emphasis on science and technology in American schools. With a sense of urgency, Congress enacted the 1958 National Defense Education Act, which provided low-interest loans for college tuition to students majoring in mathematics and science. After

3762-589: The National Oceanic and Atmospheric Administration (NOAA) platforms. The latter measures the reflectance of the planet in red and near-infrared bands, as well as in the thermal infrared. In parallel, NASA developed the Earth Resources Technology Satellite (ERTS), which became the precursor to the Landsat program . These early sensors had minimal spectral resolution, but tended to include bands in

3876-658: The Soil-Adjusted Vegetation Index , the Atmospherically Resistant Vegetation Index and the Global Environment Monitoring Index. Each of these attempted to include intrinsic correction(s) for one or more perturbing factors. A current alternative adopted by USGS is the enhanced vegetation index (EVI), correcting for soil effects, canopy background, and aerosol influences. It is not until the mid-1990s, however, that

3990-516: The USSR Academy of Sciences ' mainframe computer . The Sputnik rocket was launched on 4 October 1957 at 19:28:34 UTC (5 October at the launch site ) from Site No.1 at NIIP-5. Telemetry indicated that the strap-ons separated 116 seconds into the flight and the core stage engine shut down 295.4 seconds into the flight. At shutdown, the 7.5-tonne core stage (with PS-1 attached) had attained an altitude of 223 km (139 mi) above sea level,

4104-431: The euphotic depth in the ocean. In these contexts, the reason PAR is preferred over other lighting metrics such as luminous flux and illuminance is that these measures are based on human perception of brightness , which is strongly green biased and does not accurately describe the quantity of light usable for photosynthesis. When measuring the irradiance of PAR, values are expressed using units of energy (W/m ), which

4218-405: The near-infrared . These bacteria live in environments such as the bottom of stagnant ponds, sediment and ocean depths. Because of their pigments , they form colorful mats of green, red and purple. Chlorophyll , the most abundant plant pigment, is most efficient in capturing red and blue light. Accessory pigments such as carotenes and xanthophylls harvest some green light and pass it on to

4332-471: The All-Union Research Institute of Power Sources (VNIIT) under the leadership of Nikolai S. Lidorenko. Two of these batteries powered the radio transmitter and one powered the temperature regulation system. The batteries had an expected lifetime of two weeks, and operated for 22 days. The power supply was turned on automatically at the moment of the satellite's separation from the second stage of

4446-479: The Antenna Laboratory of OKB-1, led by Mikhail V. Krayushkin. Each antenna was made up of two whip-like parts, 2.4 and 2.9 metres (7.9 and 9.5 ft) in length, and had an almost spherical radiation pattern . The power supply , with a mass of 51 kg (112 lb), was in the shape of an octagonal nut with the radio transmitter in its hole. It consisted of three silver-zinc batteries , developed at

4560-420: The Earth. Organized through the citizen science project Operation Moonwatch , teams of visual observers at 150 stations in the United States and other countries were alerted during the night to watch for the satellite at dawn and during the evening twilight as it passed overhead. The USSR requested amateur and professional radio operators to tape record the signal being transmitted from the satellite. One of

4674-576: The Moon. They decided to develop a three-stage version of the R-7 rocket for satellite launches. On 30 January 1956, the Council of Ministers approved practical work on an artificial Earth-orbiting satellite. This satellite, named Object D , was planned to be completed in 1957–58; it would have a mass of 1,000 to 1,400 kg (2,200 to 3,100 lb) and would carry 200 to 300 kg (440 to 660 lb) of scientific instruments. The first test launch of "Object D"

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4788-430: The NDVI, it remains a valuable quantitative vegetation monitoring tool when the photosynthetic capacity of the land surface needs to be studied at the appropriate spatial scale for various phenomena. Within precision agriculture , NDVI data provides a measurement of crop health. Today, this often involves agricultural drones , which are paired with NDVI to compare data and recognize crop health issues. One example of this

4902-647: The Naval Research Laboratory captured recordings of Sputnik 1 during four crossings over the United States. The USAF Cambridge Research Center collaborated with Bendix-Friez , Westinghouse Broadcasting , and the Smithsonian Astrophysical Observatory to obtain a video of Sputnik's rocket body crossing the pre-dawn sky of Baltimore, broadcast on 12 October by WBZ-TV in Boston. The success of Sputnik 1 seemed to have changed minds around

5016-775: The PPF and YPF of seven common radiation sources with a spectroradiometer, then compared with measurements from six quantum sensors designed to measure PPF, and three quantum sensors designed to measure YPF. They found that the PPF and YPF sensors were the least accurate for narrow-band sources (narrow spectrum of light) and most accurate for broad-band sources (fuller spectra of light). They found that PPF sensors were significantly more accurate under metal halide, low-pressure sodium and high-pressure sodium lamps than YPF sensors (>9% difference). Both YPF and PPF sensors were very inaccurate (>18% error) when used to measure light from red-light-emitting diodes. Photobiologically Active Radiation (PBAR)

5130-627: The Photosynthetic Photon Flux Density (PPFD). Values of PPFD are normally expressed using units of mol⋅m ⋅s . In relation to plant growth and morphology, it is better to characterise the light availability for plants by means of the Daily Light Integral (DLI), which is the daily flux of photons per ground area, and includes both diurnal variation as well as variation in day length. PPFD used to sometimes be expressed using einstein units , i.e., μE⋅m ⋅s , although this usage

5244-570: The R-7's capabilities by information derived from U-2 spy plane overflight photos, as well as signals and telemetry intercepts. General James M. Gavin wrote in 1958 that he had predicted to the Army Scientific Advisory Panel on 12 September 1957 that the Soviets would launch a satellite within 30 days, and that on 4 October he and Wernher von Braun had agreed that a launch was imminent. The Eisenhower administration's first response

5358-582: The United States as the technological superpower, and the Soviet Union as a backward country. Privately, however, the CIA and President Eisenhower were aware of progress being made by the Soviets on Sputnik from secret spy plane imagery. Together with the Jet Propulsion Laboratory (JPL), the Army Ballistic Missile Agency built Explorer 1 , and launched it on 31 January 1958. Before work

5472-399: The United States as woefully behind. One of the many books that suddenly appeared for the lay-audience noted seven points of "impact" upon the nation: Western leadership, Western strategy and tactics, missile production, applied research, basic research, education, and democratic culture. As public and the government became interested in space and related science and technology, the phenomenon

5586-449: The West. When the Soviets began using Sputnik in their propaganda, they emphasized pride in the achievement of Soviet technology, arguing that it demonstrated the Soviets' superiority over the West. People were encouraged to listen to Sputnik's signals on the radio and to look out for Sputnik in the night sky. While Sputnik itself had been highly polished, its small size made it barely visible to

5700-487: The YPF curve was developed from short-term measurements made on single leaves in low light. More recent longer-term studies with whole plants in higher light indicate that light quality may have a smaller effect on plant growth rate than light quantity. Blue light, while not delivering as many photons per joule, encourages leaf growth and affects other outcomes. The conversion between energy-based PAR and photon-based PAR depends on

5814-486: The actual usefulness of this index if they are not properly addressed. The following subsections review some of these issues. Also, the calculation of the NDVI value turns out to be sensitive to a number of perturbing factors including A number of derivatives and alternatives to NDVI have been proposed in the scientific literature to address these limitations, including the Perpendicular Vegetation Index,

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5928-447: The amount of radiation reaching a plant in the PAR region of the spectrum, it is also important to consider the quality of such radiation. Radiation reaching a plant contains entropy as well as energy, and combining those two concepts the exergy can be determined. This sort of analysis is known as exergy analysis or second law analysis, and the exergy represents a measure of the useful work, i.e.,

6042-596: The arrival of the Space Age . However, when the USSR launched Sputnik 2 , containing the dog Laika , the media narrative returned to one of anti-Communism and many people sent protests to the Soviet embassy and the RSPCA. Sputnik 1 was not immediately used for Soviet propaganda. The Soviets had kept quiet about their earlier accomplishments in rocketry, fearing that it would lead to secrets being revealed and failures being exploited by

6156-423: The biophysical characteristics of the rangeland vegetation of this region from the satellite spectral signals was confounded by these differences in solar zenith angle across this strong latitudinal gradient. With the assistance of a resident mathematician (Dr. John Schell), they studied solutions to this dilemma and subsequently developed the ratio of the difference of the red and infrared radiances over their sum as

6270-451: The booster in order to increase its visibility for tracking. A small highly polished sphere, the satellite was barely visible at sixth magnitude, and thus harder to follow optically. The batteries ran out on 26 October 1957, after the satellite completed 326 orbits. The core stage of the R-7 remained in orbit for two months until 2 December 1957, while Sputnik 1 orbited for three months, until 4 January 1958, having completed 1,440 orbits of

6384-413: The booster, and a new payload fairing that made the booster almost four meters shorter than its ICBM version. Object D would later be launched as Sputnik 3 after the much lighter 'Object PS' (Sputnik 1) was launched first. The trajectory of the launch vehicle and the satellite were initially calculated using arithmometers and six-digit trigonometric tables. More complex calculations were carried out on

6498-491: The complex, heavy scientific equipment in favour of a simple radio transmitter. On 15 February 1957 the Council of Ministers of the USSR approved this simple satellite, designated 'Object PS', PS meaning "prosteishiy sputnik", or "elementary satellite". This version allowed the satellite to be tracked visually by Earth-based observers, and it could transmit tracking signals to ground-based receiving stations. The launch of two satellites, PS-1 and PS-2, with two R-7 rockets (8K71),

6612-567: The construction of the site began on 20 July by military building units. The first launch of an R-7 rocket (8K71 No.5L) occurred on 15 May 1957. A fire began in the Blok D strap-on almost immediately at liftoff, but the booster continued flying until 98 seconds after launch when the strap-on broke away and the vehicle crashed 400 km (250 mi) downrange. Three attempts to launch the second rocket (8K71 No.6) were made on 10–11 June, but an assembly defect prevented launch. The unsuccessful launch of

6726-567: The design and operation of dedicated meteorological satellites . These are orbiting platforms embarking instruments specially designed to observe the Earth's atmosphere and surface with a view to improve weather forecasting . Starting in 1960, the TIROS series of satellites embarked television cameras and radiometers. This was later (1964 onwards) followed by the Nimbus satellites and the family of Advanced Very High Resolution Radiometer instruments on board

6840-602: The difference/sum ratio formulation as the normalized difference vegetation index. The earliest reported use of NDVI in the Great Plains study was in 1973 by Rouse et al. (Dr. John Rouse was the Director of the Remote Sensing Center of Texas A&M University where the Great Plains study was conducted). However, they were preceded in formulating a normalized difference spectral index by Kriegler et al. in 1969. Soon after

6954-496: The dummy warhead to the target altitude and velocity, reentered the atmosphere, and broke apart at a height of 10 km (6.2 mi) after traveling 6,000 km (3,700 mi). On 27 August, the TASS issued a statement on the successful launch of a long-distance multistage ICBM. The launch of the fifth R-7 rocket (8K71 No.9), on 7 September, was also successful, but the dummy was also destroyed on atmospheric re-entry, and hence needed

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7068-459: The exact spectrum of the light is known, the photosynthetic photon flux density (PPFD) values in μmol⋅s ⋅m ) can be modified by applying different weighting factors to different wavelengths. This results in a quantity called the yield photon flux (YPF). The red curve in the graph shows that photons around 610 nm (orange-red) have the highest amount of photosynthesis per photon. However, because short-wavelength photons carry more energy per photon,

7182-495: The expression above, the optimal efficiency or second law efficiency for the conversion of radiation to work in the PAR region (from λ 1 = {\displaystyle \lambda _{1}=} 400 nm to λ 2 = {\displaystyle \lambda _{2}=} 700 nm), for a blackbody at T {\displaystyle T} = 5800 K and an organism at T 0 {\displaystyle T_{0}} = 300 K

7296-496: The fact that the plant is emitting radiation. Naming x = h c λ k T {\displaystyle x={\frac {hc}{\lambda kT}}} and y = h c λ k T 0 {\displaystyle y={\frac {hc}{\lambda kT_{0}}}} , the exergy emissive power of radiation in a region is determined as: Where L i s ( z ) {\displaystyle \mathrm {Li} _{s}(z)}

7410-415: The fan was turned on; when it fell below 20 °C (68 °F), the fan was turned off by the dual thermal switch. If the temperature exceeded 50 °C (122 °F) or fell below 0 °C (32 °F), another control thermal switch was activated, changing the duration of the radio signal pulses. Sputnik 1 was filled with dry nitrogen , pressurized to 1.3  atm (130 kPa). The satellite had

7524-404: The feasibility to detect vegetation had been demonstrated, users tended to also use the NDVI to quantify the photosynthetic capacity of plant canopies. This, however, can be a rather more complex undertaking if not done properly, as is discussed below. Live green plants absorb solar radiation in the photosynthetically active radiation (PAR) spectral region, which they use as a source of energy in

7638-440: The first layer of photosynthetic cells because of chlorophyll absorbance. Green light, however, penetrates deeper into the leaf interior and can drive photosynthesis more efficiently than red light. Because green and yellow wavelengths can transmit through chlorophyll and the entire leaf itself, they play a crucial role in growth beneath the plant canopy. PAR measurement is used in agriculture, forestry and oceanography. One of

7752-619: The first observations of it in the western world were made at the school observatory in Rodewisch ( Saxony ). News reports at the time pointed out that "anyone possessing a short wave receiver can hear the new Russian earth satellite as it hurtles over this area of the globe." Directions, provided by the American Radio Relay League , were to "Tune in 20 megacycles sharply, by the time signals, given on that frequency. Then tune to slightly higher frequencies. The 'beep, beep' sound of

7866-499: 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". The R-7 core stage, with a mass of 7.5 tonnes and a length of 26 metres, also reached Earth orbit. It was a first magnitude object following behind the satellite and visible at night. Deployable reflective panels were placed on

7980-588: The hydrogen bomb payload would be. The R-7 was also known by its GRAU (later GURVO, the Russian abbreviation for "Chief Directorate of the Rocket Forces") designation 8K71. At the time, the R-7 was known to NATO sources as the T-3 or M-104, and Type A. Several modifications were made to the R-7 rocket to adapt it to 'Object D', including upgrades to the main engines, the removal of a 300 kg (660 lb) radio package on

8094-607: The launch of America's secret WS-117L spy satellites, the U.S. had launched Project Vanguard as its own "civilian" satellite entry for the International Geophysical Year. Eisenhower greatly underestimated the reaction of the American public, who were shocked by the launch of Sputnik and by the televised failure of the Vanguard Test Vehicle 3 launch attempt. The sense of anxiety was inflamed by Democratic politicians and professional cold warriors, who portrayed

8208-434: The launch of ERTS-1 (Landsat-1), Compton Tucker of NASA's Goddard Space Flight Center produced a series of early scientific journal articles describing uses of the NDVI. Thus, NDVI was one of the most successful of many attempts to simply and quickly identify vegetated areas and their "condition," and it remains the most well-known and used index to detect live green plant canopies in multispectral remote sensing data. Once

8322-472: The launch of Sputnik, a poll conducted and published by the University of Michigan showed that 26% of Americans surveyed thought that Russian sciences and engineering were superior to that of the United States. (A year later, however, that figure had dropped to 10% as the U.S. began launching its own satellites into space.) One consequence of the Sputnik shock was the perception of a " missile gap ". This became

8436-518: The launch site would be collected at six separate observatories and telegraphed to NII-4 . Located back in Moscow (at Bolshevo ), NII-4 was a scientific research arm of the Ministry of Defence that was dedicated to missile development. The six observatories were clustered around the launch site, with the closest situated 1 km (0.62 mi) from the launch pad. A second, nationwide observation complex

8550-455: The leaves, on the other hand, strongly reflects near-infrared light (from 700 to 1100 nm). The more leaves a plant has, the more these wavelengths of light are affected. Since early instruments of Earth Observation, such as NASA 's ERTS and NOAA 's AVHRR, acquired data in visible and near-infrared, it was natural to exploit the strong differences in plant reflectance to determine their spatial distribution in these satellite images. The NDVI

8664-660: The low specific impulse produced by the completed R-7 engines (304 seconds instead of the planned 309 to 310 seconds). Consequently, the government rescheduled the launch for April 1958. Object D would later fly as Sputnik 3 . Fearing the U.S. would launch a satellite before the USSR, OKB-1 suggested the creation and launch of a satellite in April–May 1957, before the IGY began in July 1957. The new satellite would be simple, light (100 kg or 220 lb), and easy to construct, forgoing

8778-514: The maximum amount of photosynthesis per incident unit of energy is at a longer wavelength, around 650 nm (deep red). It has been noted that there is considerable misunderstanding over the effect of light quality on plant growth. Many manufacturers claim significantly increased plant growth due to light quality (high YPF). The YPF curve indicates that orange and red photons between 600 and 630 nm can result in 20 to 30% more photosynthesis than blue or cyan photons between 400 and 540 nm. But

8892-439: The military to education systems. The federal government began investing in science, engineering, and mathematics at all levels of education. An advanced research group was assembled for military purposes. These research groups developed weapons such as ICBMs and missile defense systems, as well as spy satellites for the U.S. Initially, U.S. President Dwight Eisenhower was not surprised by Sputnik 1. He had been forewarned of

9006-545: The mission. A fuel regulator in the booster also failed around 16 seconds into launch, which resulted in excessive RP-1 consumption for most of the powered flight and the engine thrust being 4% above nominal. Core stage cutoff was intended for T+296 seconds, but the premature propellant depletion caused thrust termination to occur one second earlier when a sensor detected overspeed of the empty RP-1 turbopump. There were 375 kg (827 lb) of LOX remaining at cutoff. At 19.9 seconds after engine cut-off, PS-1 separated from

9120-422: The multispectral cameras and can be implemented effectively in the crop health monitoring systems. Landsat 8 , Sentinel-2 and PlanetScope are some of the main providers of satellite imagery to make NDVI maps and monitor crop health. Sputnik 1 Sputnik 1 ( / ˈ s p ʌ t n ɪ k , ˈ s p ʊ t n ɪ k / , Russian : Спутник-1 , Satellite 1 ), sometimes referred to as simply Sputnik ,

9234-463: The naked eye. What most watchers actually saw was the much more visible 26-metre core stage of the R-7. Shortly after the launch of PS-1, Khrushchev pressed Korolev to launch another satellite to coincide with the 40th anniversary of the October Revolution , on 7 November 1957. The launch of Sputnik 1 surprised the American public, and shattered the perception created by American propaganda of

9348-448: The photosynthetic process, but enough of the green wavelengths are reflected to give leaves their characteristic color. An exception to the predominance of chlorophyll is autumn, when chlorophyll is degraded (because it contains N and Mg ) but the accessory pigments are not (because they only contain C , H and O ) and remain in the leaf producing red, yellow and orange leaves. In land plants, leaves absorb mostly red and blue light in

9462-420: The process of photosynthesis . Leaf cells have also evolved to re-emit solar radiation in the near-infrared spectral region (which carries approximately half of the total incoming solar energy), because the photon energy at wavelengths longer than about 700 nanometers is too low to synthesize organic molecules. A strong absorption at these wavelengths would only result in overheating the plant and possibly damaging

9576-565: The process of photosynthesis . This spectral region corresponds more or less with the range of light visible to the human eye. Photons at shorter wavelengths tend to be so energetic that they can be damaging to cells and tissues, but are mostly filtered out by the ozone layer in the stratosphere . Photons at longer wavelengths do not carry enough energy to allow photosynthesis to take place. Other living organisms, such as cyanobacteria , purple bacteria , and heliobacteria , can exploit solar light in slightly extended spectral regions, such as

9690-417: The proving ground and preparations for the launch of PS-1 began. Compared to the military R-7 test vehicles, the mass of 8K71PS was reduced from 280 to 272 tonnes (617,000 to 600,000 lb), its length with PS-1 was 29.167 metres (95 ft 8.3 in) and the thrust at liftoff was 3.90  MN (880,000  lb f ). PS-1 was not designed to be controlled; it could only be observed. Initial data at

9804-404: The red and near-infrared, which are useful to distinguish vegetation and clouds, amongst other targets. With the launch of the first ERTS satellite – which was soon to be renamed Landsat 1 – on July 23, 1972 with its MultiSpectral Scanner (MSS) NASA funded a number of investigations to determine its capabilities for Earth remote sensing . One of those early studies was directed toward examining

9918-471: The requirements for productive farmland is adequate PAR, so PAR is used to evaluate agricultural investment potential. PAR sensors stationed at various levels of the forest canopy measure the pattern of PAR availability and utilization. Photosynthetic rate and related parameters can be measured non-destructively using a photosynthesis system , and these instruments measure PAR and sometimes control PAR at set intensities. PAR measurements are also used to calculate

10032-498: The rocket. The satellite had a one-watt, 3.5 kg (7.7 lb) radio transmitting unit inside, developed by Vyacheslav I. Lappo from NII-885 , the Moscow Electronics Research Institute, that worked on two frequencies, 20.005 and 40.002 MHz. Signals on the first frequency were transmitted in 0.3 s pulses (near f = 3 Hz) (under normal temperature and pressure conditions on board), with pauses of

10146-418: The same duration filled by pulses on the second frequency. Analysis of the radio signals was used to gather information about the electron density of the ionosphere. Temperature and pressure were encoded in the duration of radio beeps. A temperature regulation system contained a fan , a dual thermal switch , and a control thermal switch. If the temperature inside the satellite exceeded 36 °C (97 °F),

10260-463: The satellite can be heard each time it rounds the globe." The first recording of Sputnik 1's signal was made by RCA engineers near Riverhead, Long Island. They then drove the tape recording into Manhattan for broadcast to the public over NBC radio. However, as Sputnik rose higher over the East Coast, its signal was picked up by W2AEE, the ham radio station of Columbia University . Students working in

10374-453: The second stage and the satellite's transmitter was activated. These signals were detected at the IP-1 station by Junior Engineer-Lieutenant V.G. Borisov, where reception of Sputnik 1's "beep-beep-beep" tones confirmed the satellite's successful deployment. Reception lasted for two minutes, until PS-1 passed below the horizon. The Tral telemetry system on the R-7 core stage continued to transmit and

10488-485: The spectrum of the light source (see Photosynthetic efficiency ). The following table shows the conversion factors from watts for black-body spectra that are truncated to the range 400–700 nm. It also shows the luminous efficacy for these light sources and the fraction of a real black-body radiator that is emitted as PAR. For example, a light source of 1000 lm at a color temperature of 5800 K would emit approximately 1000/265 = 3.8 W of PAR, which

10602-402: The spent R-7 second stage at the same time as the satellite was ejected. Tests of the satellite were conducted at OKB-1 under the leadership of Oleg G. Ivanovsky . The control system of the Sputnik rocket was adjusted to an intended orbit of 223 by 1,450 km (139 by 901 mi), with an orbital period of 101.5 minutes. The trajectory had been calculated earlier by Georgi Grechko , using

10716-632: The spring vegetation green-up and subsequent summer and fall dry-down (the so-called “vernal advancement and retrogradation”) throughout the north to south expanse of the Great Plains region of the central U.S. This region covered a wide range of latitudes from the southern tip of Texas to the U.S.-Canada border, which resulted in a wide range of solar zenith angles at the time of the satellite observations. The researchers for this Great Plains study (PhD student Donald Deering and his advisor Dr. Robert Hass) found that their ability to correlate, or quantify,

10830-418: The third R-7 rocket (8K71 No.7) took place on 12 July. An electrical short caused the vernier engines to put the missile into an uncontrolled roll which resulted in all of the strap-ons separating 33 seconds into the launch. The R-7 crashed about 7 km (4.3 mi) from the pad. The launch of the fourth rocket (8K71 No.8), on 21 August at 15:25 Moscow Time , was successful. The rocket's core boosted

10944-404: The tissues. Hence, live green plants appear relatively dark in the PAR and relatively bright in the near-infrared. By contrast, clouds and snow tend to be rather bright in the red (as well as other visible wavelengths) and quite dark in the near-infrared. The pigment in plant leaves, chlorophyll, strongly absorbs visible light (from 400 to 700 nm) for use in photosynthesis. The cell structure of

11058-460: The transmitter batteries depleted on 26 October 1957. On 4 January 1958, after three months in orbit, Sputnik 1 burned up while reentering Earth's atmosphere , having completed 1,440 orbits of the Earth, and travelling a distance of approximately 70,000,000 km (43,000,000 mi). Спутник-1 , romanized as Sputnik-Odin ( pronounced [ˈsputnʲɪk.ɐˈdʲin] ), means 'Satellite-One'. The Russian word for satellite, sputnik ,

11172-566: The university's FM station, WKCR , made a tape of this, and were the first to rebroadcast the Sputnik signal to the American public (or whoever could receive the FM station). The Soviet Union agreed to transmit on frequencies that worked with the United States' existing infrastructure, but later announced the lower frequencies. Asserting that the launch "did not come as a surprise", the White House refused to comment on any military aspects. On 5 October,

11286-514: The useful part of radiation which can be transformed into other forms of energy. The spectral distribution of the exergy of radiation is defined as: One of the advantages of working with the exergy is that it depends not only on the temperature of the emitter (the Sun), T {\displaystyle T} , but also on the temperature of the receiving body (the plant), T 0 {\displaystyle T_{0}} , i.e., it includes

11400-537: The world regarding a shift in power to the Soviets. The USSR's launch of Sputnik 1 spurred the United States to create the Advanced Research Projects Agency (ARPA, later DARPA ) in February 1958 to regain a technological lead. In Britain, the media and population initially reacted with a mixture of fear for the future, but also amazement about human progress. Many newspapers and magazines heralded

11514-437: Was a 585-millimetre (23.0 in) diameter sphere, assembled from two hemispheres that were hermetically sealed with O-rings and connected by 36 bolts . It had a mass of 83.6 kilograms (184 lb). The hemispheres were 2 mm thick, and were covered with a highly polished 1 mm-thick heat shield made of an aluminium – magnesium – titanium alloy , AMG6T . The satellite carried two pairs of antennas designed by

11628-520: Was approved, provided that the R-7 completed at least two successful test flights. The R-7 rocket was initially designed as an intercontinental ballistic missile (ICBM) by OKB-1. The decision to build it was made by the Central Committee of the Communist Party of the Soviet Union and the Council of Ministers of the USSR on 20 May 1954. The rocket was the most powerful in the world; it was designed with excess thrust since they were unsure how heavy

11742-546: Was bestowed with the specific proper name 'Fellow-Traveler-One', rather than being designated by the general term 'Satellite-One'. In Russian-language references, Sputnik 1 is recognized by the technical name of 'Satellite-One'. On 17 December 1954, chief Soviet rocket scientist Sergei Korolev proposed a developmental plan for an artificial satellite to the Minister of the Defense Industry, Dimitri Ustinov . Korolev forwarded

11856-467: Was coined in the 18th century by combining the prefix s- ('fellow') and putnik ('traveler'), thereby meaning 'fellow-traveler', a meaning corresponding to the Latin root satelles ('guard, attendant or companion'), which is the origin of English satellite . In English, 'Sputnik' is widely recognized as a proper name; however, this is not the case in Russian. In the Russian language, sputnik

11970-467: Was completed, however, the Soviet Union launched a second satellite, Sputnik 2, on 3 November 1957. Meanwhile, the televised failure of Vanguard TV-3 on 6 December 1957 deepened American dismay over the country's position in the Space Race . The Americans took a more aggressive stance in the emerging space race, resulting in an emphasis on science and technological research, and reforms in many areas from

12084-414: Was detected on its second orbit. The designers, engineers, and technicians who developed the rocket and satellite watched the launch from the range. After the launch they drove to the mobile radio station to listen for signals from the satellite. They waited about 90 minutes to ensure that the satellite had made one orbit and was transmitting before Korolev called Soviet premier Nikita Khrushchev . On

12198-540: Was easily detectable by amateur radio operators, and the 65° orbital inclination made its flight path cover virtually the entire inhabited Earth. The satellite's success was unanticipated by the United States . This precipitated the American Sputnik crisis and triggered the Space Race . The launch was the beginning of a new era of political, military, technological, and scientific developments. The word sputnik

12312-889: Was established to track the satellite after its separation from the rocket. Called the Command-Measurement Complex, it consisted of the coordination center in NII-4 and seven distant stations situated along the line of the satellite's ground track . These tracking stations were located at Tyuratam , Sary-Shagan , Yeniseysk , Klyuchi , Yelizovo , Makat in Guryev Oblast , and Ishkup in Krasnoyarsk Krai . Stations were equipped with radar , optical instruments, and communications systems. Data from stations were transmitted by telegraphs into NII-4 where ballistics specialists calculated orbital parameters. The observatories used

12426-655: Was located and tracked by the British using the Lovell Telescope at the Jodrell Bank Observatory , the only telescope in the world able to do so by radar. Canada's Newbrook Observatory was the first facility in North America to photograph Sputnik 1. Sputnik 1 was designed to meet a set of guidelines and objectives such as: The chief constructor of Sputnik 1 at OKB-1 was Mikhail S. Khomyakov. The satellite

12540-423: Was low-key and almost dismissive. Eisenhower was even pleased that the USSR, not the U.S., would be the first to test the waters of the still-uncertain legal status of orbital satellite overflights . Eisenhower had suffered the Soviet protests and shoot-downs of Project Genetrix (Moby Dick) balloons and was concerned about the probability of a U-2 being shot down. To set a precedent for "freedom of space" before

12654-500: Was moved by the launch of Sputnik to think of space as being the next step for America. Astronauts Alan Shepard (who was the first American in space) and Deke Slayton later wrote of how the sight of Sputnik 1 passing overhead inspired them to their new careers. Photosynthetically active radiation Photosynthetically active radiation ( PAR ) designates the spectral range (wave band) of solar radiation from 400 to 700 nanometers that photosynthetic organisms are able to use in

12768-439: Was scheduled for 1957. Work on the satellite was to be divided among institutions as follows: Preliminary design work was completed in July 1956 and the scientific tasks to be carried out by the satellite were defined. These included measuring the density of the atmosphere and its ion composition, the solar wind , magnetic fields , and cosmic rays . These data would be valuable in the creation of future artificial satellites;

12882-678: Was sometimes dubbed the "Sputnik craze". The U.S. soon had a number of successful satellites, including Explorer 1, Project SCORE , and Courier 1B . However, public reaction to the Sputnik crisis spurred America to action in the Space Race, leading to the creation of both the Advanced Research Projects Agency (renamed the Defense Advanced Research Projects Agency, or DARPA, in 1972), and NASA (through

12996-561: Was the first artificial Earth satellite . It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957 as part of the Soviet space program . It sent a radio signal back to Earth for three weeks before its three silver-zinc batteries became depleted. Aerodynamic drag caused it to fall back into the atmosphere on 4 January 1958. It was a polished metal sphere 58 cm (23 in) in diameter with four external radio antennas to broadcast radio pulses. Its radio signal

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