ESA officially extended Ulysses' mission on 1 October 1995, renaming this portion as the Second Solar Orbit. Three times during its mission, the spacecraft unexpectedly passed through comet tails—the first time in May 1996 (Comet C/1996 B2 Hyakutake), the second time in 1999 (Comet C/1999 T1 McNaught-Hartley), and the third time in 2007 (Comet C/2006 P1 McNaught). The spacecraft made a second pass over the solar south pole between September 2000 and January 2001 and the northern pole between September and December 2001. At the time, the Sun was at the peak of its 11-year cycle; Ulysses found that the southern magnetic pole was much more dynamic than the north pole and lacked any fixed clear location. ESA's Science Program Committee, during a meeting on 5–6 June 2000, agreed to extend the Ulysses mission from the end of 2001 to 30 September 2004. In 2003–2004, Ulysses spun out towards its aphelion (furthest point in its orbit) and made distant observations of Jupiter. ESA's Science Program Committee approved a fourth extension of the Ulysses mission so that it could continue investigations over the Sun's poles in 2007 and 2008.

In early 2008, ESA and NASA announced that the mission would finally terminate within the subsequent few months, having operated more than four times its design life. With communications systems failing as well as power depleting due to the decline of the RTGs (and thus allowing the hydrazine fuel in its attitude control system to freeze), the spacecraft was on its last breath at that point. Mission operations continued at reduced capacity until loss of contact on 30 June 2009, more than 18.5 years after launch. Ulysses' principal findings include data that showed that there is a weakening of the solar wind over time (which was at a 50-year low in 2008), that the solar magnetic field at the poles is much weaker than previously assumed, that the Sun's magnetic field "reverses" in direction every 11 years, and that small dust particles coming in from deep space into the solar system are 30 times more abundant than previously assumed.

Geotail

Nation: USA/Japan (1) Objective(s): high elliptical Earth orbit Spacecraft: Geotail Spacecraft Mass: 1,009 kg Mission Design and Management: ISAS / NASA Launch Vehicle: Delta 6925 (no. D212) Launch Date and Time: 24 July 1992 / 14:26 UT Launch Site: Cape Canaveral Air Force Station / Launch Complex 17A

Scientific Instruments:

magnetic fields measurement monitor (MGF)
low energy particles experiment (LEP)
electric field monitor (EFD)
energetic particles and ion composition experiment (EPIC)
high-energy particle monitors (HEP)
plasma wave instrument (PWI)
comprehensive plasma instrument (CPI)

Results: The Geotail mission was a joint project of Japan's ISAS (and later, from 2003, JAXA), and NASA, executed as part of the International Solar Terrestrial Physics (ISTP) project, which also included the later Wind, Polar, SOHO, and Cluster missions. This particular mission's goal was to study the structure and dynamics of the long tail region of Earth's magnetosphere, which is created on the nightside of Earth by the solar wind. During active periods, the tail couples with the near-Earth magnetosphere, and often releases energy that is stored in the tail, thus activating auroras in the polar ionosphere. Although technically not a deep space or planetary mission, Geotail, in its extremely elliptical orbit, performed numerous lunar flybys, some closer than the distance at which the Soviet Luna 3 took the first pictures of the farside of the Moon.

The spin-stabilized spacecraft (20 rpms) was designed with a pair of 100-meter tip-to-tip antennae and two 6-meter-long masts. On its fifth orbit around Earth, near apogee, on 8 September 1992, the spacecraft flew by the Moon at a range of 12,647 kilometers. The flyby raised apogee from 426,756 kilometers to 869,170 kilometers. Such flybys continued almost every month subsequent to that, and ultimately raised the spacecraft's apogee to 1.4 million kilometers. During these orbits, Geotail observed the magnetotail's far region (from 80 to 220 times the radius of Earth or "Re"). Geotail's 14th and last flyby of the Moon occurred on 25 October 1994 at a range of 22,445 kilometers and as a result, placed the spacecraft in orbits with progressively lower apogees. In November 1994, Geotail's apogee was 50 Re and by February 1995, it was down to 30 Re. The lower orbit was designed to allow the spacecraft to begin the second part of its mission, to study magnetotail sub-storms near Earth. During these orbits, perigee was about 10 Re, while the orbital inclination to the ecliptic plane was about –7° in order that the apogee would be located in the magnetotail's neutral plane during the winter solstice. Later in the decade, Geotail's orbit was adjusted so that it passed just inside Earth's magnetosphere's boundary plane on the dayside. In 2012, the spacecraft celebrated twenty years of continuous operation, and in 2014, despite having an original lifetime of only four years, was still sending back data on the formation of auroras, the nature of energy funneled from the Sun into near-Earth space, and the ways in which Earth's magnetic field lines move and rebound, thus producing explosive bursts that affect our magnetic environment.

Mars Observer

Nation: USA (65) Objective(s): Mars orbit Spacecraft: Mars Observer Spacecraft Mass: 1,018 kg Mission Design and Management: NASA / JPL Launch Vehicle: Titan III (CT-4) Launch Date and Time: 25 September 1992 / 17:05:01 UT Launch Site: Cape Canaveral Air Force Station / Space Launch Complex-40

Scientific Instruments:

Mars Observer camera (MOC)
thermal emission spectrometer (TES)
pressure modulator infrared radiometer (PMIRR)
Mars Observer laser altimeter (MOLA)
magnetometer/electron reflectometer (MAG/ER)
gamma-ray spectrometer (GRS)
radio science experiment (RS)
Mars balloon relay receiver (MBR)

Results: Mars Observer was designed to carry out a high-resolution photography mission of the Red Planet over the course of a Martian year (687 days) from a 378 × 350-kilometer polar orbit. Building on the research done by the Viking missions, it carried a suite of instruments to investigate Martian geology, atmosphere, and climate in order to fill in gaps on our knowledge of planetary evolution. A mere 31 minutes after launch, the new Transfer Orbit Stage (TOS), using the Orbus 21 solid rocket motor, fired to boost the spacecraft on an encounter trajectory with Mars. After a 725 million-kilometer voyage lasting 11 months, at 00:40 UT on 22 August 1993, just two days prior to planned entry into Mars orbit, the spacecraft stopped sending telemetry (as planned), but then never resumed 14 minutes later. Despite vigorous efforts to regain contact, Mars Observer remained quiet.

When the spacecraft did not reestablish command as a result of a stored program that was designed to do so in case of five days of silence, mission planners finally gave up hope on salvaging the mission. The results of a five-month investigation proved to be inconclusive, but one likely cause of the catastrophic failure may have been a fuel line rupture that could have damaged the spacecraft's electronics, throwing the vehicle into a spin. In addition, the fact that the Mars Observer bus was a repurposed Earth science satellite bus may have also compromised the spacecraft's ability to adapt to the deep space environment. While none of the primary mission objectives were accomplished, the spacecraft did return data during its interplanetary cruise. Scientific instruments developed for Mars Observer were later used on several subsequent Mars probes, including Mars Global Surveyor (launched in 1996), Mars Climate Orbiter (1998), Mars Odyssey (2001), and Mars Reconnaissance Orbiter (2005).

Clementine

Nation: USA (66) Objective(s): lunar orbit Spacecraft: Clementine Spacecraft Mass: 424 kg Mission Design and Management: BMDO / NASA Launch Vehicle: Titan IIG (no. 23G-11) Launch Date and Time: 25 January 1994 / 16:34 UT Launch Site: Vandenberg AFB / SLC-4W

Scientific Instruments:

ultraviolet/visible camera (UV/Vis)
near-infrared camera (NIR)
laser image detection and ranging system (LIDAR)
long-wave infrared camera (LWIR)
high-resolution camera (HIRES)
2 star tracker cameras
bistatic radar experiment
S-band transponder Doppler gravity experiment
charged particle telescope (CPT)

Results: Clementine was the first U.S. spacecraft launched to the Moon in over 20 years (since Explorer 49 in June 1973). The spacecraft, also known as the Deep Space Program Science Experiment (DSPSE), was designed and built to demonstrate a set of lightweight technologies such as small-imaging sensors and lightweight gallium arsenide solar panels for future low-cost missions flown by the Department of Defense. Specifically, Clementine was a technology proving mission for the DOD's Brilliant Pebbles program for the Strategic Defense Initiative (SDI), which required a large fleet of inexpensive spacecraft. Clementine carried 15 advanced flight-test components and 9 science instruments.

After launch, the spacecraft remained in a temporary parking orbit until 3 February 1994, at which time a solid-propellant rocket ignited to send the vehicle to the Moon. After two subsequent Earth flybys on 5 and 15 February, on 19 February Clementine successfully entered an elliptical polar orbit (430 × 2,950 kilometers) around the Moon with a period of five days. In the following two months, it transmitted about 1.6 million digital images of the lunar surface, many of them with resolutions down to 100–200 meters, in the process, providing scientists with their first look at the total lunar landscape including polar regions. After completing its mission goals over 297 orbits around lunar orbit, controllers fired Clementine's thrusters on 3 May to inject it on a rendezvous trajectory (via an Earth flyby) with the asteroid 1620 Geographos in August 1994.

However, due to a computer problem at 14:39 UT on 7 May that caused a thruster to fire and use up all propellant, the spacecraft was put in an uncontrollable tumble at about 80 rpms with no spin control. Controllers were forced to cancel the asteroid flyby and return the vehicle to the vicinity of Earth. A power supply problem further diminished the operating capacity of the vehicle. Eventually, on 20 July, lunar gravity took control of Clementine and propelled it into heliocentric orbit. The mission was terminated on 8 August when falling power supply levels no longer allowed clear telemetry exchange. Surprisingly, because the spacecraft was fortuitously in the correct attitude to power up again, ground controllers were able to briefly regain contact between 20 February and 10 May 1995. On 3 December 1996, the Department of Defense announced that Clementine data indicated that there was ice in the bottom of a permanently shadowed crater on the lunar south pole. Scientists estimated the deposit to be approximately 60,000 to 120,000 cubic meters in volume, i.e., comparable to a small lake that is four football fields in surface area and 5 meters deep. This estimate was very uncertain, however, due to the nature of the data. An accounting of Clementine's legacy should include the fact that methods developed for the project became the basis for NASA's "Faster, Better, Cheaper" initiative which ultimately paved the way for the Agency's Discovery program.

Wind

Nation: USA (67) Objective(s): Sun–Earth L1 Lagrange Point Spacecraft: Wind Spacecraft Mass: 1,250 kg Mission Design and Management: NASA / GSFC Launch Vehicle: Delta 7925-10 (no. D227) Launch Date and Time: 1 November 1994 / 09:31:00 UT Launch Site: Cape Canaveral Air Force Station / Launch Complex 17B

Scientific Instruments:

radio and plasma wave experiment (WAVES)
energetic particle acceleration, composition, and transport experiment (EPACT)
solar wind and suprathermal ion composition experiment (SMS)
- solar wind ion composition spectrometer (SWICS)
- high mass resolution spectrometer (MASS)
- suprathermal ion composition spectrometer (STICS)
solar wind experiment (SWE)
2 triaxial fluxgate magnetometers (MFI magnetic field investigation)
three-dimensional plasma and energetic particle investigation (3DP)
transient gamma-ray spectrometer (TGRS)
Konus gamma-ray burst studies experiment

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