ULA Atlas V launches NASA’s Juno on a path to Jupiter

by William Graham

United Launch Alliance (ULA) have launched their Atlas V carrying NASA’s Juno probe on its way to Jupiter on Friday. The liftoff of the flagship mission was delayed by 51 minutes, due to a ground leak and a boat in the range box, prior to launching at 12:25 local time. Juno will become the first spacecraft to orbit Jupiter since the Galileo probe was deorbited in 2003.

Flagship Mission To Jupiter:

Juno is the second mission in NASA’s New Frontiers programme. The first mission, New Horizons, is currently on its way to Pluto and the Kuiper Belt. It is expected to fly past Pluto and its four moons in July 2015. A third mission, OSIRIS-REx, is expected to be launched in 2016. It will study the asteroid 1999 RQ36 before returning a sample to Earth. The New Frontiers programme calls for medium-class spacecraft for planetary exploration.

The Juno spacecraft was built by Lockheed Martin for NASA’s Jet Propulsion Laboratory. It has a spin stabilised configuration, with a mass of 3,625 kilograms. Unlike previous missions to the outer planets, which have used Radioisotope Thermoelectric Generators (RTGs) for power, Juno will be powered by three solar panels, each measuring 2.65 metres in width, and 8.9 metres in length when fully deployed. A LEROS-1b engine will be used for course corrections and orbital insertion.

Juno carries nine instruments. The Microwave Radiometer (MWR) will be used to study heat being emitted from Jupiter in order to study the dynamics and composition of its atmosphere. The Jovian Infrared Auroral Mapper (JIRAM) will conduct infrared observation and spectroscopic analysis of the upper levels of Jupiter’s atmosphere, which will also help scientists to understand the structure of the atmosphere.

The Flux Gate Magnetometer (FGM) will be used to produce a map of Jupiter’s magnetic field, and to study how the magnetosphere is structured in the planet’s polar regions. Studies of the magnetic field will also aid investigations into the internal dynamics of the planet. The Advanced Stellar Compass (ASC) will help with the mapping by allowing Juno to plot its position accurately.

Juno’s Polar Magnetosphere Suite of instruments consists of the Juno Energetic Particle Detector Instrument (JEDI), the Jovian Auroral Distributions Experiment (JADE), the Ultraviolet Spectrometer (UVS), the Radio and Plasma Waves Experiment, or WAVES, as well as JIRAM.

This combined set of instruments will study electric currents flowing along field lines in the planet’s magnetic field, and ultraviolet and electromagnetic emissions and the distribution of energetic particles in Jupiter’s aurorae.

JADE will study the energy and distribution of particles in the polar regions of Jupiter’s magnetosphere, whilst JEDI will study the energy and distribution of ions, particularly hydrogen, helium, oxygen and sulphur, to see if there is any change over time. WAVES will look for currents within the aurora, and compare them to Jupiter’s radio emissions to establish how the currents affect the emissions. UVS will record data on incident ultraviolet radiation.

JunoCam (JCM) will produce three-colour images of Jupiter, which will be used for visual studies of Jupiter, giving context to other observations, and for public release.

As part of a public outreach programme, three Lego figurines are being carried aboard the spacecraft, depicting the Roman god Jupiter, the goddess Juno, and seventeenth-century Italian astronomer Galileo Galilei.

A plaque donated by the Italian Space Agency with an image of Galileo and some text from one of his observations of Jupiter has been attached to the spacecraft’s propulsion system.

The spacecraft is named Juno after the Roman goddess of marriage, and wife of the god Jupiter. According to Roman mythology Jupiter hid himself in clouds, however Juno was able to see through those clouds, and uncover the truth about Jupiter.

In addition to these instruments, Juno will also use its communications systems to study Jupiter’s gravitational field, as part of the Gravity Science Experiment. By transmitting signals to Earth and studying their Doppler shift, scientists hope to be able to study how Jupiter’s gravity affects Juno, and hence gain a greater understanding of the internal structure of the planet.

Following launch, Juno will take five years to reach Jupiter. Two years into its journey, in October 2013, it will return to Earth for a flyby which will provide a gravitational assist, propelling it into the outer solar system. In August 2016 Juno will enter Jovian, or zenocentric, orbit, beginning fourteen months of studying Jupiter from orbit. Juno is intended to operate in a polar orbit around Jupiter.

Juno will be the ninth spacecraft to visit the planet Jupiter. Named after the Roman god of the sky, Jupiter is almost 318 times more massive than Earth, and over 1,300 times larger in terms of volume. It orbits the Sun at a radius of 5.2 astronomical units, completing one orbit every 4331 days. A gas giant, it is comprised of about 90 percent hydrogen and 10 percent helium, with trace amounts of other gases, including methane and ammonia.

Jupiter has 64 known natural satellites, and four rings. Its largest satellites are the four Galilean Moons, which were discovered in 1609 or 1610 by Galileo Galilei. These were the first objects to be discovered orbiting a celestial body other than the Earth, and helped to disprove the geocentric model of the cosmos.

Jupiter itself is covered in bands of clouds containing crystallised ammonia, with wind speeds of around 100 metres per second. The Great Red Spot, a storm two or three times the size of Earth, is one of the most well-known and long-lasting features in Jupiter’s atmosphere, having been observed for over 180 years. Smaller storms have also been observed, including a second red spot; Oval BA, also known as Red Spot Junior, which was formed in 2000 by the collision of three other storms.

The first spacecraft to visit Jupiter was Pioneer 10, which was launched on 3 March 1972 aboard an Atlas LV-3C Centaur-D with a Star-37E kick motor. It flew past Jupiter and its Galilean Moons in December 1973; reaching a closest approach of around 200,000 kilometres at 02:26 UTC on 4 December.

Pioneer 10 was also the first spacecraft to achieve solar escape velocity, and since passing Jupiter it has continued on its way out of the solar system. The last transmission detected from it was received on 23 January 2003, at a distance of over 80 astronomical units.

Pioneer 11 was launched on the maiden flight of the Atlas SLV-3D Centaur-D1A on 6 April 1973, also equipped with a Star-37E kick motor.

It flew past Jupiter in December 1974, and at 05:21 UTC on 3 December, it made its closest approach. Using a gravitational assist from Jupiter, it flew on towards Saturn, before also leaving the solar system.

The two Pioneer missions to the outer solar system paved the way for the Voyager programme; an offshoot of the Mariner programme which saw two more missions to Jupiter launched by larger Titan IIIE rockets, again using Star-37E kick motors. Both of these missions were launched from Launch Complex 41 at Cape Canaveral, the same launch complex from which Juno will depart today.

Voyager 2 was launched on 20 August 1977, with Voyager 1 on 5 September. Voyager 1 followed a different trajectory to Voyager 2, and was ahead of its sister craft by the end of the year. It reached Jupiter in March 1989, following two months of observing the planet as it approached.

At 12:05 UTC on 5 March, it passed Jupiter at a distance of 348,890 kilometres. Observations of Jupiter continued until 13 March, as Voyager 1 flew away from Jupiter en route to its November 1980 encounter with Saturn.

On 25 April, less than a fortnight after Voyager 1 ceased its observations of Jupiter, Voyager 2 began to make distant observations. A little over two months later, at 22:29 on 9 July, Voyager 2 made its closest approach of 721,760 kilometres from Jupiter.

Like its predecessor, it continued to make observations as it departed towards Saturn, ending on 5 August. Voyager 2 went on to fly past Saturn, Uranus and Neptune, becoming the only spacecraft to date to visit all four outer planets.

The Ulysses spacecraft, which was deployed from Space Shuttle Discovery during the STS-41 mission in October 1990 by means of an Inertial Upper Stage (IUS), flew past Jupiter on 8 February 1992.

Ulysses was a mission to study the Sun, and its visit to Jupiter was not primarily to study the planet, but to gain a gravitational assist which increased its orbital inclination.

Despite this, Ulysses did take readings of Jupiter’s magnetosphere during the flyby. Ulysses made a second, distant, flyby of Jupiter in 2004 during which it took more readings. The spacecraft was finally deactivated on 30 June 2009.

Galileo was the first mission to place a spacecraft into orbit around Jupiter. It also carried an atmospheric probe which became the first spacecraft to enter Jupiter’s atmosphere.

Launched aboard Space Shuttle Atlantis on 18 October 1989 during the STS-34 mission, and successfully deployed less than seven hours later, Galileo was propelled into heliocentric orbit by means of an Inertial Upper Stage.

Galileo had originally been intended to be deployed using a Centaur-G upper stage during the STS-61-G mission.

The Shuttle-Centaur programme was cancelled after the loss of Challenger due to concerns about crew safety in the event of a launch abort, and as a result the Galileo mission had to be redesigned for deployment with the less powerful IUS.

This necessitated the spacecraft making a flyby of Venus, and two of Earth, before finally arriving at Jupiter. En route, it flew past the asteroids 951 Gaspra and 243 Ida. During the flyby of Ida it discovered Dactyl, the first natural satellite to be found orbiting an asteroid.

On 13 July 1995, an atmospheric probe was released from Galileo. It entered the atmosphere of Jupiter on 7 December, after which it operated for 58 minutes before it overheated, or was crushed under the pressure of Jupiter’s atmosphere. The first data returned by the probe arrived at 22:15 UTC, however given the distance between Jupiter and Earth; this would have been transmitted several minutes earlier.

At 02:10 UTC on 8 December, the Galileo spacecraft was confirmed to be in orbit around Jupiter, after a signal was received confirming the end of its orbital insertion burn.

Galileo remained in orbit of Jupiter for over seven years and nine months, during which time it made many discoveries, including the structure of the planet’s rings, the presence of a magnetic field around the moon Ganymede and the possible existence of a subsurface ocean on the moon Europa.

On 21 September 2003 Galileo was deorbited in order to prevent a possible collision with one of Jupiter’s natural satellites, which could have led to contamination. Galileo entered Jupiter’s atmosphere at 18:57 UTC following a slingshot around the moon Amalthea the previous November.

Cassini flew past Jupiter on 30 December 2000, gaining a gravity assist for its journey to Saturn. At the time, Cassini was a little under halfway to Saturn, having been launched aboard a Titan IV(401)B rocket on 15 October 1997, and finally entering orbit around Saturn on 1 July 2004.

During the flyby the spacecraft produced 26,000 images of Jupiter, including some of the most detailed pictures ever returned of the planet. Studies of the data and images returned by Cassini helped scientists to understand more clearly the weather patterns and circulation within Jupiter’s atmosphere.

New Horizons was the most recent spacecraft to visit Jupiter, flying past in February 2007 to pick up a gravity assist for its mission to the dwarf planet Pluto. New Horizons was launched by an Atlas V 551 with a Star-48B kick motor from SLC-41 on 19 January 2006, at which time Pluto was still considered a planet.

During its flyby of Jupiter, which reached closest approach at 05:43 UTC on 28 February 2007, New Horizons produced images of the planet, its satellites and rings, and recorded data on its magnetosphere.

Juno launched atop Atlas V AV-029, which flew in the 551 configuration, with a five metre payload fairing, five solid rocket motors augmenting the first stage, and a single-engined Centaur (SEC) second stage. This was the second time the 551 configuration has flown; its previous launch being that of New Horizons. In total, it is the twenty seventh launch of an Atlas V.

The five metre payload fairing has an exact external diameter of 5.4 metres, and is available three different lengths. The “short” fairing is 20.7 metres long, whilst the “medium” length is 23.4 metres, and a “long” fairing 26.5 metres long. The five metre fairings are produced by RUAG, a Swiss company which also produces a similar fairing for the Ariane 5 rocket.

Juno was encapsulated in a “short” fairing, the length which has been used for all Atlas V launches with five metre fairings, except for the NROL-41 mission last September, which used the “medium” fairing.

The launch of Juno was  the 175th flight of an Atlas rocket with a Centaur upper stage. The Atlas-Centaur began flying in May 1962, with its maiden flight ending in failure.

Consisting of an Atlas intercontinental ballistic missile boosting a Centaur cryogenically-propelled upper stage, the Atlas-Centaur retained the Atlas missile’s unusual first stage configuration, with two of its three first stage engines on a detachable booster unit which would be jettisoned to save weight when those engines were no longer needed. The third, sustainer, engine would then power the first stage alone for the remainder of its burn.

The first successful launch of an Atlas Centaur occurred in November 1963, placing a mock-up payload into orbit. It marked the first time a rocket powered in part by liquid hydrogen had reached orbit. Despite this success, four of the first five launches ended in failure, including the AC-5 test flight which fell back onto its launch pad and exploded after an engine failure two seconds after liftoff, resulting in a fireball which caused significant damage to the launch complex.

Eventually the Atlas-Centaur became a successful and reliable launch system, and by the time the Atlas SLV-3D Centaur-D1AR, the last variant to be explicitly named Atlas-Centaur, made its final flight in May 1983, it had achieved 51 successful launches from 61 attempts. The Atlas SLV-3D Centaur-D1AR was replaced by the Atlas G, which used the same Centaur-D1AR, but with a stretched first stage. It made seven launches between 1984 and 1989 with two failures.

The Atlas I was the first member of the Atlas family to be identified using a numeral rather than a letter. Essentially identical to the Atlas G, it featured improved guidance systems, including digital components. Operated between July 1990 and April 1997, eleven were launched with three failures.

The Atlas I was replaced by the more capable Atlas II, which featured a stretched first stage and a stretched Centaur, as well as more powerful engines on the first stage and booster unit. The Atlas II first flew in December 1991, with the Atlas IIA; a variant with uprated Centaur engines, making its first flight in June 1992.

A third variant, the Atlas IIAS, which featured four Castor-4A solid rocket motors augmenting the first stage, began flying in December 1993. In all, the three Atlas II variants made 63 launches, all of which were successful. The last, an Atlas IIAS, was launched on 31 August 2004.

The Atlas III was a short-lived rocket, operated from May 2000 to February 2005. The Atlas IIIA offered a similar payload capacity to the Atlas IIAS, whilst the Atlas IIIB had a greater capacity through use of a stretched Centaur.

It bridged the gap between the Atlas II and the Atlas V; introducing a conventional first stage design, the Russian-built RD-180 main engine, and the single-engine Centaur upper stage for all Atlas IIIA launches, and as an option for the Atlas IIIB. Two Atlas IIIAs were launched, along with one Atlas IIIB with a conventional twin-engine Centaur, and three IIIBs with the newer single-engine model.

The Atlas V made its maiden flight on 21 August 2002, carrying the Hot Bird 6 satellite for Eutelsat. It introduced multiple configurations, with four and five metre fairings, any number between zero and five boosters, and single of dual engine Centaur upper stages.

To date, all launches have used the single-engine Centaur, and a dual-engined version has not yet been developed, however following Thursday’s announcement that the Atlas V 412 configuration would be used to launch Boeing’s CST-100 spacecraft from 2015, a dual engine Centaur will now need to be developed.

The first stage of the Atlas V is the Common Core Booster (CCB). Like the Common Booster Cores used on the Delta IV, the CCB was designed to be stacked in parallel, allowing a “Heavy” Atlas V with three CCBs. This has never flown, with development being abandoned in favour of the Delta IV Heavy. It is possible; however, that it may be needed to support manned commercial missions in the future.

The Common Core Booster is fuelled by RP-1 propellant, oxidised by liquid oxygen. A single RD-180 engine powers the stage. The Centaur second stage is powered by an RL10A-4-2 burning liquid hydrogen in liquid oxygen. The five solid rocket motors were manufactured by Aerojet, and provide an average of around 1.1 meganewtons of thrust each.

The launch of Juno began with the ignition of the RD-180 main engine, 2.7 seconds before the countdown reached zero. At T-0, the solid rocket motors ignited, and about 1.1 seconds later AV-029 began a fast climb away from Cape Canaveral. A second after liftoff, the vehicle reached maximum thrust, and after another 1.7 seconds it began to manoeuvre to the correct attitude for its ascent to orbit.

About 34.5 seconds into its mission, AV-029 passed through Mach 1, beginning supersonic flight. A little under twelve seconds later it experienced Max-Q, the area of maximum dynamic pressure. The solid boosters burnt out 85 to 90 seconds after launch, and 104 seconds into the flight they were jettisoned.

Three minutes and 24.9 seconds into the flight, the payload fairing separated from around Juno. After this, the forward load reactor, which helps to dampen vibrations within the fairing, was also jettisoned. Around 233 seconds after launch the RD-180 engine throttled down to maintain a constant acceleration of 5G, in order to limit stresses on the payload.

Booster Engine Cutoff, the end of first stage flight, came with the depletion of the CCBs propellant, about four minutes and 27.2 seconds after launch. Six seconds later the CCB separated from the Centaur, which ignited ten seconds after separation to begin the first of two burns. This first burn lasted five minutes and fifty eight seconds.

Once the burn was complete, the Centaur entered a coast phase lasting thirty minutes, 48.2 seconds. The second and last Centaur burn was then performed, lasting nine minutes and seven tenths of a second. With the final burn complete AV-029 manoeuvred to the correct attitude for spacecraft separation, which came 53 minutes, 49.2 seconds into the mission.

AV-029 was the fiftieth rocket to be launched from Space Launch Complex 41 at the Cape Canaveral Air Force Station. Built as a Titan IIIC launch pad in the 1960s, Launch Complex 41 was first used in December 1965. It was originally part of the Integrate-Transfer-Launch complex, along with LC-40.

Rockets were assembled in the Vertical Integration Building (VIB), and then moved to the launch pad on rails, before the payload was installed at the pad using the mobile service tower. The VIB was demolished in 2006.

Following ten Titan IIIC launches between 1965 and 1969, mostly carrying IDSCP and Vela satellites, the complex was modified to accommodate the Titan IIIE. This Titan configuration, which used a Centaur-D1T upper stage, made seven launches from LC-41, and following its failure to launch the Sphinx satellite in February 1974, the Titan IIIE successfully dispatched the Viking probes to Mars, the Voyager probes to the outer planets, and the Helios probes to study the Sun.

Following the last Titan IIIE launch in 1977, LC-41 was disused for several years, until the Titan IV programme started. Between 1989 and 1999, ten Titan IV launches were conducted from SLC-41, beginning with the type’s maiden flight on 14 June 1989. In 1997, the complex was renamed from Launch Complex 41 to Space Launch Complex 41.

The last two Titan launches from SLC-41 ended in failure; the penultimate launch was the final flight of the Titan IVA, which was flying the NROL-7 mission to deploy a Mercury signals intelligence satellite. The rocket, Titan IV(401)A A-20 or K-17, named Elwood by its launch crew after Dan Aykroyd’s character in The Blues Brothers (the Centaur was named Jake after John Belushi’s character), was destroyed by range safety 40 seconds after launch following a guidance system malfunction.

The final Titan to launch from SLC-41 was a Titan IV(402)B, carrying a Defense Support Program satellite. This vehicle, B-27 or K-32, reached orbit, and the first stage of its Inertial Upper Stage fired to place the payload into its transfer orbit; however the first and second stages of the IUS failed to separate, and upon ignition of the second stage the vehicle began to spin out of control.

The burn failed to place the spacecraft into this correct target orbit, and in addition the spacecraft sustained damage which caused a fuel line to rupture shortly after spacecraft separation.

Six months after the Titan IV made its last launch from the complex the fixed and mobile service towers were demolished, and the pad was converted for the Atlas V. The first Atlas V launch from the pad was the maiden flight, in August 2002.

The first five Atlas V launches from SLC-41 all deployed commercial communications satellites. The sixth launch deployed NASA’s Mars Reconnaissance Orbiter, and the seventh was that of the New Horizons spacecraft.

Since then, three more commercial communications satellites have been launched, in addition to NASA’s Lunar Reconnaissance Orbiter and Solar Dynamics Observatory, two X-37B flights, the mysterious USA-207 “PAN” satellite, and several military payloads for the US Air Force and National Reconnaissance Office. AV-029 is the twenty third Atlas V to fly from SLC-41; the other four were launched from SLC-3E at Vandenberg Air Force Base.

AV-029 was assembled in the Vertical Integration Facility; a tower located 550 metres southeast of Space Launch Complex 41, which is used to assemble all Atlas V rockets launched from the complex. Assembled atop a mobile launch platform, AV-029 was rolled to the launch pad Thursday, with rollout beginning at 12:01 UTC, and lasting about 39 minutes.

The local weather – as expected – was not a concern for a launch on 5 August, as much as there were some concern regarding Tropical Storm Emily.

As of Wednesday evening, the storm was about 1850 kilometres to the southeast of Cape Canaveral, moving to the west-northwest before being expected to head northwest. Due to possible landfall in the Caribbean, it was not possible to predict exactly where the storm will go, or whether it could have affected the launch. In the end, it didn’t become a factor.

This was the fourth of five Atlas V launches being conducted this year; the fifth is expected to occur in late November, with the Curiosity rover bound for Mars. Before

then, United Launch Alliance are expected to launch two Delta II rockets. A Delta II 7920H will deploy the GRAIL spacecraft in early September, and then a Delta II 7920 will launch the NPP weather satellite in late October. It still remains unclear whether or not these will be the last flights of Delta II rockets.

(Images via Larry Sullivan – MaxQ Entertainment/NASASpaceflight.com, L2 Historical’s 500gbs of hi res photos, and NASA.gov)

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