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The end of Ulysses
test of this approach in January, the power supply to the radio transmitter failed to turn back on. Engineers believe the fault can be traced to the transmitter's power supply, meaning that the extra energy they had hoped to gain cannot be routed to the heater and science instruments. According to Marsden, "The decision to switch the transmitter off was not taken lightly. It was the only way to continue the science mission".
The End of Ulysses [From NASA Press Release, 22 February 2008 supplemented by ulysses.jpl.nasa.gov, dated 15 January 2008] he joint NASA/ESA Ulysses mission to study the Sun and its influence on surrounding space is likely to cease operations in the next few months. The venerable spacecraft, which has lasted more than 17 years or almost four times its expected mission lifetime, is expected to succumb to the harsh environment of space and, in particular, to the low temperatures it experiences during its highly eccentric orbit. Since its Jupiter flyby in 1992, Ulysses has been in a six-year orbit around the Sun. Its long path through space carries it out to Jupiter's orbit and back. The further it ventures from the Sun, the colder the spacecraft becomes. If it drops to 36 degrees Fahrenheit, the spacecraft' s hydrazine fuel will freeze. Previously, this has not been a problem because Ulysses carries heaters to maintain a workable onboard temperature.
T
The spacecraft is powered by the decay of a radioactive isotope. Over its 17-plus years, the power has been steadily dropping. The spacecraft can no longer run all of its communications, heating and scientific equipment simultaneously. Richard Marsden (ESA project scientist and mission manager) commented: "We expect certain parts of the spacecraft to reach 36 degrees pretty soon". This temperature drop will block the fuel pipes, making the spacecraft impossible to manoeuvre. The NASA/ESA project team approved a plan to shut off temporarily the spacecraft's X-band transmitter. This would have released 60 watts of power, which could have been channeled to the science instruments and the heater. The team then planned to turn the transmitter back on when data was ready to be transmitted back to Earth thereby making it possible to run Ulysses for up to another two years. Unfortunately, during the first
The joint ESA/NASA mission Ulysses named after the hero of Greek legend in his Roman incarnation) charting the unknown above and below the poles of the Sun. [Courtesy: ESA.] After many attempts, the project team now considers it unlikely that the X-band transmitter will be recovered. Thus, the spacecraft has lost its ability to send large quantities of scientific data back to Earth and is facing the gradual freezing of its fuel lines. The team plans to continue operating the spacecraft in its reduced capacity, using the alternate S-band transmitter, for as long as they can over the next few weeks. "We will squeeze the very last drops of science out of it that we can" said Marsden. "Ulysses is a terrific old workhorse. It has produced great science and lasted much longer than we ever thought it would". 38
Ulysses was the first mission to survey the space environment above and below the poles of the Sun. Ed Massey (Ulysses project manager at NASA's Jet Propulsion Laboratory, Pasadena, Ca.) commented "I remember when we got those first pictures of Ulysses floating out of the space shuttle Discovery's payload bay back in October of 1990 and thinking we had a great five years ahead of us. I never dared think that we would be receiving invaluable science data on a near continuous basis for more than 17 years. Ulysses has set the bar on solar science data collection quite high".Scientific findings and discoveries from the mission have been numerous and unprecedented. Examples include taking the first direct measurements of interstellar dust particles and interstellar helium atoms in the solar system and the discovery that the magnetic field leaving the Sun is balanced across latitudes. "The data and science output of this mission truly deserves to be named after the legendary explorer in Greek mythology" said Arik Posner (Ulysses NASA programme scientist). "My compliments go to the international team of scientists and engineers who built a spaceship and instrument payload that is highly sensitive, yet durable enough that it withstood the most extreme conditions in the solar system, including a polar passage of the giant planet Jupiter".
provided a unique perspective from which to study the Sun and its effect on surrounding space.
Ulysses was built by Dornier Systems, Germany, for ESA. NASA provided the launch and upper stage boosters. The US Department of Energy supplied the generator; science instruments were provided by US and European investigators. The spacecraft is operated from JPL by a joint NASA/ESA team and has employed the Deep Space Network for communications.
India Launches Israeli Satellite [From ISRO release, January 2008] ndia has followed its first major commercial launch of its PSLV rocket (PSLV-CS), which took place on 23 April 2007, with the successful launch of an Israeli satellite. The first launch was the Italian astronomical satellite, Agile. On 21 January 2008, PSLV-C10 lifted off carrying the Tecsar satellite. This 300 kg satellite was placed into its intended orbit with a perigee of 450 km and apogee of 580 km with an inclination of 41 °. The PSLV has emerged as ISRO's workhorse launch vehicle with eleven consecutively successful flights to date. Since its first successful launch in 1994, the PSLV has launched eight Indian remote sensing satellites, an amateur radio satellite (Hamsat), a recoverable space capsule, SRE-1, and two primary satellites and six small satellites for foreign customers. It has also been used to launch India's meteorological satellite, Kalpana- 1, into Geosynchronous Transfer Orbit (GTO). The same launch vehicle is also to be used to launch India's first spacecraft to the Moon, Chandrayaan-1, later this year. Tecsar is a Synthetic Aperture Radar (SAR) technology satellite. The design, development and fabrication activities were led by MBT Space, a division of the Israeli Aerospace Industries with the participation of other high tech industries such as ELTA, Tadiran Spectralink and Rafael. The satellite is equipped with a SAR payload with the capability to carry out day and night all-weather imaging.
I
During the first Ulysses orbit, the Sun's magnetic poles were positive with outward fields in the north and negative or inward fields in the south. During its second orbit at sunspot maximum, the Sun's polar fields disappeared and then reappeared with the opposite sense, negative or inward in the north and positive or outward in the south. In addition, the strength of the polar fields was about one-half of what they had been during the first orbit. About a year after Ulysses again crossed into the Sun's south polar cap, it began its journey over the north polar cap. Previous spacecraft have remained near the Sun's equator where the Earth and the other planets are located. As Ulysses' orbit is perpendicular or highly inclined to all other spacecraft orbits, it has 39
The End of Ulysses [From NASA Press Release, 22 February 2008 supplemented by ulysses.jpl.nasa.gov, dated 15 January 2008] he joint NASA/ESA Ulysses mission to study the Sun and its influence on surrounding space is likely to cease operations in the next few months. The venerable spacecraft, which has lasted more than 17 years or almost four times its expected mission lifetime, is expected to succumb to the harsh environment of space and, in particular, to the low temperatures it experiences during its highly eccentric orbit. Since its Jupiter flyby in 1992, Ulysses has been in a six-year orbit around the Sun. Its long path through space carries it out to Jupiter's orbit and back. The further it ventures from the Sun, the colder the spacecraft becomes. If it drops to 36 degrees Fahrenheit, the spacecraft' s hydrazine fuel will freeze. Previously, this has not been a problem because Ulysses carries heaters to maintain a workable onboard temperature.
T
The spacecraft is powered by the decay of a radioactive isotope. Over its 17-plus years, the power has been steadily dropping. The spacecraft can no longer run all of its communications, heating and scientific equipment simultaneously. Richard Marsden (ESA project scientist and mission manager) commented: "We expect certain parts of the spacecraft to reach 36 degrees pretty soon". This temperature drop will block the fuel pipes, making the spacecraft impossible to manoeuvre. The NASA/ESA project team approved a plan to shut off temporarily the spacecraft's X-band transmitter. This would have released 60 watts of power, which could have been channeled to the science instruments and the heater. The team then planned to turn the transmitter back on when data was ready to be transmitted back to Earth thereby making it possible to run Ulysses for up to another two years. Unfortunately, during the first
The joint ESA/NASA mission Ulysses named after the hero of Greek legend in his Roman incarnation) charting the unknown above and below the poles of the Sun. [Courtesy: ESA.] After many attempts, the project team now considers it unlikely that the X-band transmitter will be recovered. Thus, the spacecraft has lost its ability to send large quantities of scientific data back to Earth and is facing the gradual freezing of its fuel lines. The team plans to continue operating the spacecraft in its reduced capacity, using the alternate S-band transmitter, for as long as they can over the next few weeks. "We will squeeze the very last drops of science out of it that we can" said Marsden. "Ulysses is a terrific old workhorse. It has produced great science and lasted much longer than we ever thought it would". 38
Ulysses was the first mission to survey the space environment above and below the poles of the Sun. Ed Massey (Ulysses project manager at NASA's Jet Propulsion Laboratory, Pasadena, Ca.) commented "I remember when we got those first pictures of Ulysses floating out of the space shuttle Discovery's payload bay back in October of 1990 and thinking we had a great five years ahead of us. I never dared think that we would be receiving invaluable science data on a near continuous basis for more than 17 years. Ulysses has set the bar on solar science data collection quite high".Scientific findings and discoveries from the mission have been numerous and unprecedented. Examples include taking the first direct measurements of interstellar dust particles and interstellar helium atoms in the solar system and the discovery that the magnetic field leaving the Sun is balanced across latitudes. "The data and science output of this mission truly deserves to be named after the legendary explorer in Greek mythology" said Arik Posner (Ulysses NASA programme scientist). "My compliments go to the international team of scientists and engineers who built a spaceship and instrument payload that is highly sensitive, yet durable enough that it withstood the most extreme conditions in the solar system, including a polar passage of the giant planet Jupiter".
provided a unique perspective from which to study the Sun and its effect on surrounding space.
Ulysses was built by Dornier Systems, Germany, for ESA. NASA provided the launch and upper stage boosters. The US Department of Energy supplied the generator; science instruments were provided by US and European investigators. The spacecraft is operated from JPL by a joint NASA/ESA team and has employed the Deep Space Network for communications.
India Launches Israeli Satellite [From ISRO release, January 2008] ndia has followed its first major commercial launch of its PSLV rocket (PSLV-CS), which took place on 23 April 2007, with the successful launch of an Israeli satellite. The first launch was the Italian astronomical satellite, Agile. On 21 January 2008, PSLV-C10 lifted off carrying the Tecsar satellite. This 300 kg satellite was placed into its intended orbit with a perigee of 450 km and apogee of 580 km with an inclination of 41 °. The PSLV has emerged as ISRO's workhorse launch vehicle with eleven consecutively successful flights to date. Since its first successful launch in 1994, the PSLV has launched eight Indian remote sensing satellites, an amateur radio satellite (Hamsat), a recoverable space capsule, SRE-1, and two primary satellites and six small satellites for foreign customers. It has also been used to launch India's meteorological satellite, Kalpana- 1, into Geosynchronous Transfer Orbit (GTO). The same launch vehicle is also to be used to launch India's first spacecraft to the Moon, Chandrayaan-1, later this year. Tecsar is a Synthetic Aperture Radar (SAR) technology satellite. The design, development and fabrication activities were led by MBT Space, a division of the Israeli Aerospace Industries with the participation of other high tech industries such as ELTA, Tadiran Spectralink and Rafael. The satellite is equipped with a SAR payload with the capability to carry out day and night all-weather imaging.
I
During the first Ulysses orbit, the Sun's magnetic poles were positive with outward fields in the north and negative or inward fields in the south. During its second orbit at sunspot maximum, the Sun's polar fields disappeared and then reappeared with the opposite sense, negative or inward in the north and positive or outward in the south. In addition, the strength of the polar fields was about one-half of what they had been during the first orbit. About a year after Ulysses again crossed into the Sun's south polar cap, it began its journey over the north polar cap. Previous spacecraft have remained near the Sun's equator where the Earth and the other planets are located. As Ulysses' orbit is perpendicular or highly inclined to all other spacecraft orbits, it has 39