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60-643: Explorer II was a crewed U.S. high-altitude balloon that was launched on November 11, 1935, and reached a record altitude of 22,066 m (72,395 ft). Launched at 8:00 am from the Stratobowl in South Dakota , the helium balloon carried a two-man crew consisting of U. S. Army Air Corps Captains Albert W. Stevens and Orvil A. Anderson inside a sealed, spherical cabin. The crew landed safely near White Lake, South Dakota , at 4:13 pm and both were acclaimed as national heroes. Scientific instruments carried on

120-550: A GPS receiver, an APRS encoder, and a radio transmitter module. Other experimental payload modules include an Amateur Radio crossband repeater, and a digital camera , all of which is contained within an insulated foam box suspended below the balloon. A BalloonSat is a simple package designed to carry lightweight experiments into near space. They are a popular introduction to engineering principles in some high school and college courses. BalloonSats are carried as secondary payloads on ARHAB flights. One reason BalloonSats are simple

180-598: A Global Positioning System (GPS) receiver and converts it to a digital radio transmission. Other flights may use an analog beacon and are tracked using radio direction finding techniques. Long duration flights frequently must use high frequency custom-built transmitters and slow data protocols such as radioteletype (RTTY), Hellschreiber , Morse code , and PSK31 , to transmit data over great distances using little battery power. The use of amateur radio transmitters on an ARHAB flight requires an amateur radio license, but non-amateur radio transmitters are possible to use without

240-430: A narrow line of thunderstorms can form along the frontal zone. If instability is weak, a broad shield of rain can move in behind the front , and evaporative cooling of the rain can increase the temperature difference across the front. Cold fronts are stronger in the fall and spring transition seasons and are weakest during the summer. A cold front occurs when a mass of comparatively colder air moves into where warmer air

300-419: A warm front or squall line. Very commonly, cold fronts have a warm front ahead but with a perpendicular orientation. In areas where cold fronts catch up to the warm front, the occluded front develops. Occluded fronts have an area of warm air aloft. When such a feature forms poleward of an extratropical cyclone, it is known as a trowal , which is short for TR ough O f W arm A ir a L oft. A cold front

360-476: A crew of three in an airtight capsule, along with a laboratory of instruments. The hydrogen balloon, named Explorer , was completed by July at a cost of around $ 60,000; equivalent to $ 1,366,567 in 2023 currency. The balloon was launched from a canyon in the Black Hills of South Dakota —dubbed the Stratobowl —on July 28, 1934 and reached a near-record altitude of 18,475 m (60,613 ft) before tears in

420-482: A flight attempt. A team of meteorologists was assembled at the Stratobowl in early September and they proceeded to put together a weather station. The meteorological requirements for the launch was for clear skies—with no precipitation—lasting for the duration of the flight, as well as surface wind speeds that were not to exceed 23 km/h (14 mph). With a cold front approaching, on the night of November 10, 1935,

480-472: A high-altitude balloon. Geostationary balloon satellites ( GBS ) are proposed high-altitude balloons that would float in the mid- stratosphere (60,000 to 70,000 feet (18 to 21 km) above sea level) at a fixed point over the Earth's surface and thereby act as an atmospheric satellite . At those altitudes, air density is around 1/15 to 1/20 of what it is at sea level . The average wind speed at these levels

540-584: A license. In addition to the tracking equipment, other payload components may include sensors, data loggers, cameras, amateur television (ATV) transmitters or other scientific instruments. Some ARHAB flights carry a simplified payload package called BalloonSat . A typical ARHAB flight uses a standard latex weather balloon, lasts around 2–3 hours, and reaches 25–35 km (16–22 mi) in altitude. Experiments with zero-pressure balloons , superpressure balloons , and valved latex balloons have extended flight times to more than 24 hours. A zero-pressure flight by

600-515: A new world altitude record, and one that would last for nearly two decades. The crew became the first humans to document the curvature of the Earth. Unfortunately, the fan that was to be used to rotate the gondola proved ineffective at that altitude, so they were unable to avoid the Sun's glare. This made viewing from one side of the capsule nearly useless. Despite this, Captain Stevens reported seeing details of

660-414: A platform for experiments in the upper atmosphere. Modern balloons generally contain electronic equipment such as radio transmitters , cameras , or satellite navigation systems, such as GPS receivers. Hobbyists frequently purchase weather balloons because of their ease of use, low price point, and widespread commoditisation. These balloons are launched into what is defined as " near space ", defined as

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720-602: Is a popular hobby , with organizations such as UKHAS assisting the development of payloads. In France during 1783, the first public experiment with hydrogen-filled balloons involved Jacques Charles , a French professor of physics, and the Robert brothers , renowned constructors of physics instruments. Charles provided large quantities of hydrogen , which had only been produced in small quantities previously, by mixing 540 kg (1,190 lb) of iron and 270 kg (600 lb) of sulfuric acid . The balloon took 5 days to fill and

780-466: Is a series of Canadian-based high-altitude balloon experiments by a group of Amateur Radio operators and experimenters from Sherwood Park and Edmonton, Alberta. The experiments started in the year 2000 and continued with BEAR-9 in 2012, reaching 36.010 km (22.376 mi). The balloons are made of latex filled with either helium or hydrogen . All of the BEAR payloads carry a tracking system comprising

840-452: Is less than that at the surface. A propulsion system would allow the balloon to move into and maintain its position. The GBS would be powered with solar panels. A GBS could be used to provide broadband Internet access over a large area. Laser broadband would connect the GBS to the network , which could then provide a large area of coverage because of its wider line of sight over the curvature of

900-858: Is part of a course taught by Space Grant at the University of Colorado at Boulder. Often the design of a BalloonSat is under weight and volume constraints. This encourages good engineering practices, introduces a challenge, and allows for the inclusion of many BalloonSats on an ARHAB flight. The airframe material is usually Styrofoam or Foamcore, as they are lightweight, easy to machine, and provide reasonably good insulation. Most carry sensors, data loggers and small cameras operated by timer circuits. Popular sensors include air temperature, relative humidity, tilt, and acceleration. Experiments carried inside BalloonSats have included such things as captive insects and food items. Before launch, most BalloonSats are required to undergo testing. These tests are designed to ensure

960-438: Is present. The drier, colder air forms a steeply sloping boundary under the warmer, moister air at the surface and lifts that air. This often causes cloud formations with a strong vertical development, which may manifest as a line of showers and thunderstorms when enough moisture is present. On weather maps , the surface position of the cold front is marked with the symbol of a blue line of triangles/spikes (pips) pointing in

1020-498: Is sufficient moisture. If the cold front is highly unstable , cumulonimbus clouds producing thunderstorms commonly form along the front. Anvil cirrus clouds may spread a considerable distance downwind from the thunderstorms. The other cloud types associated with a cold front depend on atmospheric conditions such as airmass stability and wind shear. As the front approaches, middle-étage gives way to altostratus and low-level stratocumulus with intermittent light precipitation if

1080-546: Is that they do not require the inclusion of tracking equipment; as secondary payloads, they already are being carried by tracking capsules. Space Grant started the BalloonSat program in August 2000. It was created as a hands-on way to introduce new science and engineering students interested in space studies to some fundamental engineering techniques, team working skills and the basics of space and Earth science. The BalloonSat program

1140-404: Is the application of analog and digital amateur radio to weather balloons and was the name suggested by Ralph Wallio (amateur radio callsign W0RPK) for this hobby. Often referred to as "The Poor Man's Space Program", ARHAB allows amateurs to design functioning models of spacecraft and launch them into a space-like environment. Bill Brown (amateur radio callsign WB8ELK) is considered to have begun

1200-420: Is the process of creating or steepening the temperature gradient of a front. During this process the atmosphere reacts in an attempt to restore balance, the consequence is a circular motion along the front where air is being lifted up, along the cold front and dropping downward, behind the frontal boundary. This is the actual force of upward motion along a front that is responsible for clouds and precipitation. As

1260-736: The Hubbard Medal of the National Geographic Society by General John J. Pershing . The Air Corps awarded them the Mackay Trophy for the most meritorious flight of the year. Both men were also awarded the Distinguished Flying Cross for each of the Explorer flights. Scientific observations made during the mission were highly successful and much data was collected, with the results appearing in scientific journals. The data and

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1320-658: The Mediterranean Sea . The flight lasted 57 hours and 2 minutes. It became the first successful U.S. transcontinental and the first successful transatlantic amateur radio high-altitude balloon. Since that time, a number of flights have circumnavigated the Earth using superpressure plastic film balloons. Each year in the United States, the Great Plains Super Launch (GPSL) hosts a large gathering of ARHAB groups. Balloon Experiments with Amateur Radio (BEAR)

1380-568: The Spirit of Knoxville Balloon Program in March 2008 lasted over 40 hours and landed off the coast of Ireland, over 5,400 km (3,400 mi) from its launch point. On December 11, 2011, the California Near Space Project flight number CNSP-11 with the call sign K6RPT-11 launched a record-breaking flight traveling 6,236 mi (10,036 km) from San Jose, California , to a splashdown in

1440-526: The BalloonSat crew can prepare the BalloonSat at the launch site. Besides conducting scientific activities, schools, influencers and other individuals have launched a wide variety of novelty payloads to the stratosphere with high-altitude balloons. These have included teddy bears, LEGO figurines, hamburgers, pizza, Cornish pasties , garlic bread , bacon and cans of beer. Japanese electronics manufacturer Toshiba attempted to record an advertisement in near space with an armchair and cameras tethered to

1500-418: The BalloonSat will function properly and return science results. The tests include a cold soak, drop test, function test, and weighing. The cold soak test simulates the intense cold temperatures the BalloonSat will experience during its mission. A launch and landing can be traumatic, therefore the drop test requires the BalloonSat to hold together and still function after an abrupt drop. The function test verifies

1560-470: The Earth and unimpeded Fresnel zone . World View Enterprises built and operates a balloon spaceport (high-altitude balloon port) in Pima County, Arizona . Cold front A cold front is the leading edge of a cooler mass of air at ground level that replaces a warmer mass of air and lies within a pronounced surface trough of low pressure . It often forms behind an extratropical cyclone (to

1620-482: The Earth's surface for hundreds of miles. They were too high up to be able to view any movement on the ground, but their photography showed the potential of high-altitude reconnaissance balloons . Explorer II included communications equipment, and constant radio contact was maintained throughout the flight with the signal being broadcast across the U.S. and in Europe. The onboard instruments collected data on cosmic rays ,

1680-517: The NGS sobered by the risk. A review of the crash by the National Bureau of Standards (NBS) was held between July and September, revealing that the balloon had not opened symmetrically during the ascent, causing stresses that led to the fabric tears. A month-long delay prior to launch had allowed the rubberized cotton to stick together, which created the uneven expansion. The hydrogen explosion followed when

1740-1080: The Soviet Osoaviakhim-1 at 22,000 m (22.0 km), and the American Explorer II at 22,066 m (22.1 km). Notable crewed high altitude balloon flights include three records set for highest skydive: Uncrewed high-altitude balloons are used as research balloons , for educational purposes, and by hobbyists. Common uses include meteorology, atmospheric and climate research, collection of imagery from near space, amateur radio applications, and submillimetre astronomy . High-altitude balloons have been considered for use in telecommunications and space tourism . Private companies such as Zero 2 Infinity , Space Perspective , Zephalto , and World View Enterprises are developing both crewed and uncrewed high-altitude balloons for scientific research, commercial purposes, and space tourism. High-altitude platform stations have been proposed for applications such as communications relays. In many countries,

1800-530: The airmass behind the front remains humid from a source of moisture. Small and unchanging amounts of cumulus or cirrus clouds in an otherwise clear sky are usually indications of continuing fair weather as long as the barometric pressure remains comparatively high. A cold front commonly brings a narrow band of precipitation that follows along the leading edge of the cold front. These bands of precipitation are often very strong, and can bring severe thunderstorms, hailstorms , snow squalls, and/or tornadoes . In

1860-539: The area of Earth's atmosphere between the Armstrong limit (18–19 km (11–12 mi) above sea level), where pressure falls to the point that a human being cannot survive without a pressurised suit, and the Kármán line (100 km (62 mi) above sea level ), where astrodynamics must take over from aerodynamics in order to maintain flight. Due to the low cost of GPS and communications equipment, high-altitude ballooning

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1920-593: The balloon stood 96 m (316 ft) tall. The gondola was kept anchored to the earth by a team of more than 100 soldiers holding cables. Preparations were complete by 7:01 am the following morning and the conditions were deemed suitable for a launch. The crew of the Explorer II consisted of Captain Albert W. Stevens, in command of the mission, and Captain Orvil A. Anderson . A crowd of around 20,000 viewers gathered to watch

1980-422: The balloon was prepared for launch. The temperature dropped to −14 °C (6 °F) overnight, so the 10,762.4 m (115,845 sq ft) of fabric was kept warm and pliable through the use of stoves. The task of inflating the balloon with helium from the 1,685 steel cylinders took eight hours, during which the team needed to repair a 5.2 m (17 ft) long tear that formed in the fabric. Once inflated,

2040-475: The boundary. In the northern hemisphere, a cold front usually causes a shift of wind from southwest to northwest clockwise, also known as veering, and in the southern hemisphere a shift from northwest to southwest (counterclockwise, backing). Atmospheric pressure steadily decreases with the approach of a cold front. With frontal passage, the pressure rises sharply and then stabilizes. Normally, cold fronts can be marked by these characteristics: *provided there

2100-565: The bureaucratic overhead required for high altitude balloon launches is minimal when the payload is below a certain weight threshold, typically on the order of a few kilograms. This makes the process of launching these small HABs accessible to many students and amateur groups. Despite their smaller size, these HABs still often ascend to (and past) altitudes on the order of 30,000 m (98,000 ft), providing easy stratospheric access for scientific and educational purposes. These amateur balloon flights are often informed in their operations by

2160-613: The crew experiences were later used when designing flight crew equipment and methods for high-altitude combat operations during World War II . The balloon used for the Explorer II expedition was cut up into a million strips and distributed as commemorative bookmarks among the NGS members who supported the mission. The gondola is on display at the Smithsonian Institution 's National Air and Space Museum . High-altitude balloon The most common type of high-altitude balloons are weather balloons . Other purposes include use as

2220-419: The direction of travel. A cold front's location is at the leading edge of the temperature drop off, which in an isotherm analysis would show up as the leading edge of the isotherm gradient, and it normally lies within a sharp surface trough . Cold fronts move faster than warm fronts and can produce sharper changes in weather. Since cold air is denser than warm air, it rapidly replaces the warm air preceding

2280-455: The event. (The local residents had raised and contributed $ 13,000 for the mission.) Lift-off occurred at precisely 8:00 am with the release of 34 kg (75 lb) of ballast made of fine lead shot. A few moments after liftoff, wind shear propelled the balloon into a side canyon, but thereafter it ascended normally. The Explorer II reached a peak altitude of 22,066 m (72,395 ft) at 12:30 pm and remained there for 80 minutes. This set

2340-404: The fabric led the crew to begin reducing their altitude. A rupture in the balloon resulted in a precipitous descent, followed by a spark that caused the hydrogen to ignite and destroy what was left of the balloon, leaving the capsule to plummet toward the ground at terminal velocity . The crew just managed to escape using their parachutes, with the last man bailing out at 500 feet (150 m) above

2400-520: The first launch occurred July 10, 1935. Unfortunately, this too proved a failure with the balloon rupturing at liftoff. Following a review by the NBS, the balloon was prepared for another attempt after Goodyear strengthened the material. Examination of climatological data for the Stratobowl collected over the previous fifteen years was examined, and it was determined that the month of October typically had periods of good weather that would last sufficiently long for

2460-453: The front is cooler than the air it is replacing and the warm air is forced to rise, so it cools. As the cooler air cannot hold as much moisture as warm air, clouds form and rain or snow occur. Cold fronts form when a cooler air mass moves into an area of warmer air in the wake of a developing extratropical cyclone. The warmer air interacts with the cooler air mass along the boundary, and usually produces precipitation. Cold fronts often follow

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2520-405: The gas in the bag mixed with the oxygen in the atmosphere. Despite the concerns, in 1935 the NGS and Army Air Corps decided to make another attempt. To eliminate the hazard of the hydrogen lifting gas, it was decided instead to use helium—to which the United States had a monopoly. The lower lifting efficiency of helium gas meant that a larger balloon would be needed, so Goodyear-Zeppelin increased

2580-479: The gondola returned useful information about the stratosphere . The mission was funded by the membership of the National Geographic Society . In January 1934, the National Geographic Society (NGS) and the U. S. Army Air Corps decided to collaborate on a program to build and launch a manned balloon to the then record altitude of 24 km (15 mi). This vehicle would be capable of carrying

2640-588: The ground station. Smaller packages called micro or pico trackers are also built and run under smaller balloons. These smaller trackers have used Morse code , Field Hell , and RTTY to transmit their locations and other data. The first recorded amateur radio high-altitude balloon launches took place in Finland by the Ilmari program on May 28, 1967, and in Germany in 1964. Amateur radio high-altitude ballooning ( ARHAB )

2700-507: The ground. Their capsule was almost completely destroyed upon impact. The crash resulted in a national embarrassment, leading Captain Albert W. Stevens , the scientific observer on board the Explorer balloon, to lobby for another attempt with an improved balloon to be named Explorer II . But news of the fatal crash of a Russian stratospheric attempt in 1934 left President Gilbert H. Grosvenor of

2760-402: The middle of winter. Temperature changes associated with cold fronts can be as much as 30 °C (54 °F). When cold fronts come through, there is usually a quick, yet strong gust of wind, that shows that the cold front is passing. In surface weather observations , a remark known as FROPA is coded when this occurs. The effects from a cold front can last from hours to days. The air behind

2820-444: The modern ARHAB movement with his first launch of a balloon carrying an amateur radio transmitter on 15 August 1987. An ARHAB flight consists of a balloon, a recovery parachute, and a payload of one or more packages. The payload normally contains an amateur radio transmitter that permits tracking of the flight to its landing for recovery. Most flights use an Automatic Packet Reporting System (APRS) tracker which gets its position from

2880-432: The ozone distribution and electrical conductivity of the atmosphere at different altitudes, the atmospheric composition of the stratosphere, and the luminosity of the Sun, Moon and Earth. In addition, microorganisms were collected from the stratosphere. Mold samples were carried along to determine the effects of cosmic ray exposure. Stevens took along a camera to take pictures, including the first ever motion pictures shot from

2940-430: The same time, observable along the front as a thermally direct circulation. There are several factors that influence the final shape and tilt of the circulation around the front, ultimately determining the kind and location of clouds and precipitation. Cold fronts are the leading edge of cooler air masses, hence the name "cold front". They have stronger temperature changes during the fall (autumn) and spring, and during

3000-426: The spring, these cold fronts can be very strong, and can bring strong winds when the pressure gradient is higher than normal. During the winter months, cold fronts sometimes come through an area with little or no precipitation. Wider rain bands can occur behind cold fronts which tend to have more stratiform, and less convective, precipitation. These rainstorms sometimes bring flooding , and can move very slowly when

3060-476: The storm steering it is strong and embedded within a meridional flow pattern (with more pole to equator motion rather than west to east motion). In the winter, cold fronts can bring cold spells, and occasionally snow. In the spring or summer in temperate latitudes, hail may occasionally fall along with the rain. If moisture is not sufficient, such as when a system has previously moved across a mountain barrier, cold fronts can pass without cloudiness. Frontogenesis

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3120-469: The stratosphere. The collected data showed that the ozone in the upper atmosphere was effective at blocking most of the ultraviolet radiation from the Sun. It was also found that the percentage of oxygen at the peak altitude was about the same as that at sea level. Finally, the descent was begun and it proceeded normally. At an altitude of 300 m (1,000 ft), the crew began releasing scientific instruments that would descend by their own parachutes. This

3180-437: The temperature gradient steepens during frontogenesis, the thermal wind becomes imbalanced. To maintain balance, the geostrophic wind aloft and below adjust, such that regions of divergence/convergence form. Mass continuity would require a vertical transport of air along the cold front where there is divergence (lowered pressure ). Although this circulation is described by a series of processes, they are actually occurring at

3240-431: The use of a path predictor. Before launch, weather forecasts containing predicted wind vectors are used to numerically propagate a simulated HAB along a trajectory, predicting where the actual balloon will travel. Testing radio range is often a large component of these hobbies. Amateur radio is often used with packet radio to communicate with 1200 baud , using a system called Automatic Packet Reporting System back to

3300-401: The volume to 100,000 m (3,700,000 cu ft). Dow Chemical Company assembled a larger, lighter gondola made of "Dowmetal"—a magnesium-aluminium alloy— that would carry a two-man crew with a reduced amount of scientific instrumentation. The cabin was 2.7 m (9 ft) in diameter with a mass of 290 kg (640 lb) and could transport a 680 kg (1,500 lb) payload. It

3360-448: The warm airmass being displaced by the cold front is mostly stable. With significant airmass instability, vertically developed cumulus or cumulonimbus with showers and thunderstorms will form along the front. After the passage of the cold front, the sky usually clears as high pressure builds in behind the system, although significant amounts of cumulus or stratocumulus, often in the form of long bands called cloud streets , may persist if

3420-521: The west in the Northern Hemisphere , to the east in the Southern ), at the leading edge of its cold air advection pattern—known as the cyclone 's dry "conveyor belt" flow. Temperature differences across the boundary can exceed 30 °C (54 °F) from one side to the other. When enough moisture is present, rain can occur along the boundary. If there is significant instability along the boundary,

3480-420: Was done to protect the data in case the gondola had a rough landing. The precautions proved unnecessary as the balloon landed gently in an open field near the town of White Lake, South Dakota at 4:13 pm. The success of the mission was much celebrated in the press and the aeronauts were invited to an audience with U.S. President Franklin D. Roosevelt . They became national heroes and both men were presented with

3540-518: Was launched from Champ de Mars in Paris where 300,000 people gathered to watch the spectacle. The balloon was launched and rose through the clouds. The expansion of the gas caused the balloon to tear and it descended 45 minutes later 20 km (12 mi) away from Paris. Crewed high-altitude balloons have been used since the 1930s for research and in seeking flight altitude records , including Auguste Piccard's flights up to 16,201 m (16.2 km),

3600-404: Was manufactured from a single, large plate that was cut up into form that could be reshaped and welded into a sphere. In order to make crew escape easier, the portholes were made wider than on the Explorer I . The atmosphere in the interior of the capsule was supplied from liquid air instead of liquid oxygen in order to reduce the fire hazard. The modified balloon was ready by the spring of 1935 and

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