Encyclopedia Astronautica
Contour



contour.jpg
Contour
American comet probe. One launch, 2002.07.03.

NASA's Comet Nucleus Tour (CONTOUR) was designed to provide the first detailed look at the differences between these primitive building blocks of the solar system, and answer questions about how comets act and evolve. Contour's flexible four-year mission plan included encounters with comets Encke, Nov.12, 2003, and Schwassmann-Wachmann 3, June 19, 2006. It was not to be; the solid rocket motor that was to boost the spacecraft into solar orbit failed.

CONTOUR was to examine each comet's nucleus, which scientists believe was a chunk of ice and rock, often just a few kilometers across and hidden from Earth-based telescopes beneath a dusty atmosphere and long tail.

SPACECRAFT
Dimensions: 8-sided main structure; 1.8 meters (6 feet) tall; 2.1 meters (7 feet) wide
Total Weight: 970 kilograms (2,138 pounds)

  • Dry spacecraft and instruments: 387 kilograms (853 pounds)
  • STAR-30 Solid Rocket Motor: 503 kilograms (1,109 pounds)
  • Hydrazine fuel: 80 kilograms (176 pounds)
Science Instruments: high-resolution tracking imager and spectrograph; fixed visible imager; neutral gas and ion mass spectrometer; dust analyzer
Power: 9 body-mounted gallium arsenide (GaAs) solar panels; nickel-cadmium (NiCd) battery backup
Propulsion: STAR-30 Solid Rocket Motor; 16-thruster hydrazine system
Protection: Layered dust shield of Nextel and Kevlar fabric

MISSION PROFILE
Launch Vehicle: Boeing Delta II Med-Lite (7425)
Launch Site: Cape Canaveral Air Force Station, Fla.
Launch Window: July 1-25, 2002 (6-second daily launch opportunities)
Spacecraft Separation: 63 minutes, 30 seconds after launch
First Acquisition of Signal: 85 minutes after launch (Goldstone DSN station, Calif.)
Injection into Sun-Orbiting Earth-Return Trajectory: Aug. 15, 2002
Comet Encounters: Nov. 12, 2003 (2P/Encke); June 19, 2006 (73P/Schwassmann-Wachmann 3)
Earth Swingby Maneuvers: Aug. 2003, Aug. 2004, Feb. 2005, Feb. 2006
Cost: $159 million

CONTOUR MANAGEMENT
Principal Investigator: Dr. Joseph Veverka, Cornell University, Ithaca, N.Y.
Project Management, Spacecraft Development and Mission Operations: The Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
Navigation and Deep Space Network (DSN) Support: NASA Jet Propulsion Laboratory, Pasadena, Calif.
Science Team: 18 co-investigators from universities, industry and government agencies in the U.S. and Europe

MISSION PROFILE

INDIRECT LAUNCH MODE - CONTOUR was the first mission to use the Indirect Launch Mode, a clever plan to put a spacecraft into an elliptical Earth orbit for several weeks before propelling it toward its destination. This method affords use of a smaller launch vehicle and a longer launch window and provided a valuable chance to monitor the spacecraft while it was close to home. After launch CONTOUR would stay in a highly elliptical Earth orbit, from as low as 200 kilometers out to nearly 115,000 kilometers. Each orbit took 42 hours; CONTOUR would make 26 trips around Earth before the injection maneuver.

On 15 August 2002, when it would be in just the right position for the maneuver injecting it into a Sun-orbiting, Earth-return trajectory. Performed with the STAR-30 solid rocket motor - the motor's only use - the 50-second maneuver would send CONTOUR speeding from Earth at nearly 13 kilometers per second. CONTOUR would be about 225 kilometers above the Indian Ocean when the maneuver began. Throughout its mission, CONTOUR looped around the Sun and back to Earth for several gravity "swings" toward the target comets. These maneuvers changed CONTOUR's orbit and made it possible for CONTOUR to reach more than one comet without a large amount of fuel. During the first Earth swingby, in August 2003, the team would also calibrate the spacecraft's instruments by photographing the moon and "tracking" the Earth. The mission included four Earth swingby maneuvers.

CONTOUR would make the following earth gravity swings:

  • Aug. 15, 2003 - Closest Approach to Earth: 58,000 km
  • Aug. 14, 2004 - Closest Approach to Earth: 40,180 km
  • Feb. 10, 2005 - Closest Approach to Earth: 218,770 km
  • Feb. 10, 2006 - Closest Approach to Earth: 30,000 km

CONTOUR would cruise between comet encounters and Earth swingbys in a spin-stabilized "hibernation" mode, designed to help the mission reduce spacecraft operations and Deep Space Network tracking costs. CONTOUR would hibernate for nearly 65 percent of its journey. During four separate cruise periods - ranging from 120 days to 300 days - mission operators would turn off CONTOUR's instruments and most subsystems; only the command receivers, thermostatically controlled heaters and critical core components stay on. The command systems automatically monitored spacecraft status and corrected potential faults. The mission operations team stood down while the science, mission design and navigation teams conducted low-level planning activities. Ground controllers woke the spacecraft by sending "active spin mode" commands 35 days before each Earth swingby. This gave them enough time to track the spacecraft, calibrate the instruments and prepare for the swingby maneuver.

CONTOUR would get its first peek at the target comet several days before each encounter. The nucleus was still thousands of kilometers away - a mere speck against a background of stars - when the CONTOUR Forward Imager began taking pictures the navigation team would use to refine the spacecraft's path toward the comet. CONTOUR would transmit pictures and other encounter data just hours after closest approach.

TIMELINE FOR COMET ENCOUNTERS:

  • 60 to 10 days before the encounter: The mission team determined the spacecraft's orbit and check out its systems and instruments.
  • 10 days to 12 hours before: CONTOUR would take pictures and makes spectral observations of the coma. Optical navigation images - used to determine the craft's and comet's positions - were taken daily from up to 5 days before, then twice a day thereafter.
  • 12 hours before to 12 hours after: CONTOUR was in full encounter mode; all instruments were turned on and filled the spacecraft's data recorders.
  • 12 hours to 15 days after encounter: CONTOUR played back its data, sending it to the Mission Operations Center through the Deep Space Network. Five days after the encounter CONTOUR changed its trajectory with a short thruster firing, and the mission team determined the spacecraft's orbit.
PLANNED ENCOUNTERS

  • Encke - November 12, 2003 - Distance to sun - 1.08 AU; Distance to earth - 0.27 AU; Flybys speed 28.2 km/sec; Phase angle 12 degrees (The phase angle was the Sun-comet-CONTOUR angle. Zero degrees would mean the Sun was directly behind CONTOUR and the comet nucleus was fully lit; an angle of 180 degrees put the Sun behind the comet and the nucleus in full shadow (from CONTOUR's point of view). Low phase angles were best for viewing larger bodies; fine dust was brightest at high phase angles. )
  • SW3 - June 19, 2006 - Distance to sun - 0.96 AU; Distance to earth - 0.32AU; Flybys speed 14.0 km/sec; Phase angle 101 degrees.
  • Third target - CONTOUR's Earth-return trajectory made it possible to redirect the spacecraft toward a new comet. For instance, several additional targets were available after the SW3 encounter, including comets 6P/d'Arrest and 46P/Wirtanen. More importantly, CONTOUR's flexibility allowed it a rare opportunity to catch up with a bright, long-period comet that approached the Sun from the Oort Cloud, like Hale-Bopp in 1997. To find suitable candidates as early as possible, CONTOUR supported a worldwide "Comet Watch" program in which amateur and professional astronomers could search for candidate target comets approaching from the fringes of the solar system
SCIENCE PAYLOAD
CONTOUR's four scientific instruments would take the most detailed pictures ever of a comet nucleus, map the types of rock and ice on the nucleus, and analyze the composition of the surrounding gas and dust. The payload included:

  • CONTOUR Remote Imager and Spectrograph (CRISP) - Mass: 26.7 kilograms (59 pounds). Power: 45 watts (average). Supplier: The Johns Hopkins University Applied Physics Laboratory, Laurel, Md. CRISP combined a narrow-angle optical imager with a near-infrared spectrometer. CRISP offered top pixel scales of about 4 meters - sharp enough to pick up surface details slightly larger than an automobile - and had 10 filters for visible color study of the nucleus. The spectrometer, covering wavelengths of 780 to 2,500 nanometers, had a spatial pixel scale about three times that of the imager. Instead of facing forward, CRISP pointed out from the side of the spacecraft, so it remained protected by the dust shield. The camera's tracking mirror kept the nucleus in the field-of-view and guided the spectrometer slit across the surface, building up an infrared compositional map. It obtained its sharpest images just seconds before and after closest approach. CRISP was CONTOUR's "smartest" instrument. Scientists would load seven different imaging sequences in the camera's computer before each encounter; CRISP waited until the comet appeared from behind the dust shield, then selected the appropriate sequence for the comet's location. CRISP's computer would also direct the spacecraft to "roll" if the comet wasn't quite in its optimal field of view, and its mirror automatically tracked the nucleus for a full 30 degrees.

  • CONTOUR Forward Imager (CFI) - 9.7 kilograms (21 pounds). Power: 9 watts (average). Supplier: The Johns Hopkins University Applied Physics Laboratory. Peeking through an opening in CONTOUR's dust shield, CFI located and started taking pictures of the target comet several days before the encounter. The navigation team used these distant images to guide CONTOUR toward the nucleus, while the science team watched for phenomena in the coma. As CONTOUR sped closer to its target, CFI snapped color photos of the nucleus - capturing the movement of gas and dust jets in the inner coma - and imaged the coma in wavelengths sensitive to major species of ionized gas. Instead of pointing directly at the comet and into the stream of speeding dust, CFI's telescope looked at a mirror mounted on the side of a cube. After the mirror was peppered and pocked by particles, the cube rotated and supplied a "fresh" mirror for the next encounter.

  • Neutral Gas and Ion Mass Spectrometer (NGIMS) - Mass: 13.5 kilograms (30 pounds). Power: 36 watts (average). Supplier: NASA Goddard Space Flight Center, Greenbelt, Md. NGIMS measured the abundance of and isotope ratios for many neutral gas and ion species in each comet's coma. Combined with CIDA's dust measurements, NGIMS data would yield key information on the elemental makeup of the nucleus and allow scientists to study the chemical differences between the comets. Tracing its heritage to the Ion and Neutral Mass Spectrometer on the Saturn-bound Cassini spacecraft, NGIMS was a quadrapole mass spectrometer that employed two ion sources, each optimized for a specific set of measurements. Using both sources, NGIMS would rapidly switch between measurements of neutral gas and ambient ions in the coma as CONTOUR zipped past the nucleus. NGIMS would measure the chemical and isotopic composition of neutral and ion species over a range of 1 to 294 atomic mass units.

  • Comet Impact Dust Analyzer (CIDA) - Mass: 10.5 kilograms (23 pounds). Power: 10 watts (average). Supplier: von Hoerner & Sulger, GmbH, Schwetzingen, Germany. A copy of the Cometary and Interstellar Dust Analyzer instrument on the Stardust spacecraft, CIDA analyzed elemental and chemical composition of dust and ice grains in the comet's coma. The instrument consisted of an inlet, target, ion extractor, time-of-flight mass spectrometer and ion detector. Dust particles hit the target (a silver plate) and generated ions, which were detected by a time-of flight mass spectrometer. (Since heavier ions needed more time to move through the instrument than lighter ones, the flight times of the ions could be used to calculate their mass.) Detectable sizes range from 1 to several thousand atomic mass units, encompassing the elements and many compounds, including heavy organic molecules. Both CIDA and NGIMS would collect data continuously for several hours on either side of closest approach to the comet.

SPACECRAFT SYSTEMS AND COMPONENTS
Dust Shield - Comet dust particles were like speeding bullets to a spacecraft going 60,000 miles an hour, but CONTOUR had its own bulletproof vest: a 25-centimeter thick, layered shield of Nextel, a dense fabric like that found in firefighters' coats (among other uses). Much like the shield protecting the International Space Station, its separated layers of Nextel shatter incoming dust grains, and a Kevlar backstop absorbed remaining debris.
Electronics - CONTOUR used an APL-developed Integrated Electronics Module (IEM), a space- and weight-saving device that put a spacecraft's core avionics onto small circuit cards in a single box. CONTOUR's IEM contained 10 cards that comprised the command system, data collection and formatting system, data recorder, guidance and control processor, and X-band receiver and transmitter. CONTOUR also carried a backup IEM.

Power - CONTOUR drew power from a body-mounted, 9-panel gallium arsenide (GaAs) solar array. Maximum power depended on solar distance and angle; peak power at 1 astronomical unit (AU) was 670 watts. A 9 ampere-hour super nickel cadmium (NiCd) battery stored backup power in case the solar panels point too far off the Sun. The spacecraft was designed to operate out to 1.3 AU (195 million kilometers) from the Sun.

Propulsion - CONTOUR had a solid rocket motor and a blow-down hydrazine system. In its only use, the STAR-30 solid rocket motor provided the 1,922 meter-per-second change in velocity ("delta-v") CONTOUR needed to blast out of Earth's orbit and enter a heliocentric Earth-return trajectory on Aug. 15, 2002. The hydrazine system, used to maneuver the spacecraft for the remainder of the mission, included 16 thrusters placed in four modules of four thrusters each.

Telecommunications - CONTOUR's transceiver-based X-band communications system included an 18-inch directional high-gain dish antenna, two low-gain antennas and one pancake-beam antenna. The worldwide stations of NASA's Deep Space Network provided contact with the spacecraft after launch. CONTOUR used its high-gain antenna to send data and receive commands when 3-axis stabilized; it used a low-gain antenna when spinning in Earth orbit and between comet encounters and Earth flybys. In either mode, the spacecraft could receive commands and send data at the same time.

Command and Data Handling - CONTOUR's radiation-hardened, high-performance 32-bit Mongoose V processor received "time tagged" commands from the ground about a week (or sooner) before a scheduled maneuver or operation. Commands were normally uploaded at rates of 500 bits per second (bps), though the system could support rates of 7.8 and 125 bps. For data, CONTOUR carried two solid-state recorders (one backup) capable of storing up to 5 gigabytes each. Data and telemetry could be downlinked at rates ranging from 11 bps to 85 kilobits per second, depending on CONTOUR's distance from Earth, whether the craft was spinning or 3-axis stabilized, and whether it's communicating through the high-gain or low-gain antennas.

Guidance and Control - CONTOUR's guidance and control system included an Earth-Sun sensor, an advanced stellar compass (star tracker) and a gyroscope. When CONTOUR was 3-axis stabilized, its Mongoose V flight computer processed location and position information from the sensors to carry out specific Sun-, Earth- or comet-pointing instructions from mission operators. Ephemeris data on the positions of Earth, the Sun and the target comets was uploaded regularly into CONTOUR's flight computer. CONTOUR had no internal reaction wheels. Operators fired the hydrazine thrusters to point, spin up, spin down or otherwise move the spacecraft. The processor in CONTOUR's primary digital camera (CRISP) also "talked" directly to the flight computer during comet encounters, directing the craft to roll (if necessary) to keep the nucleus centered in the camera's tracking mirror.

Non-coherent Doppler Tracking - Deep space missions traditionally used transponders for both communication and navigation. A transponder was a "coherent" system in which the downlink frequency was based on the frequency of the uplink signal from Earth. With such a system, navigators could compare the received downlink frequency to the known transmitted uplink frequency and determine the velocity of the spacecraft (relative to Earth) from the Doppler effect. The non-coherent Doppler system on CONTOUR, however, used a transceiver in which the uplink and downlink frequencies were independent. The spacecraft used a simpler transmitter/receiver combination with an on-board oscillator. The frequency of the uplink signal received from Earth was compared to the downlink frequency at the spacecraft, and the results were put into the spacecraft's telemetry. Before performing orbit determination, navigators on Earth used this telemetered information to convert the downlinked Doppler record into what it would have been had it come from a coherent transponder. While this technique required an additional processing step relative to coherent transponding, its performance was just as accurate. It also enabled simpler, more flexible hardware to be incorporated into highly integrated electronics modules such as those flown on CONTOUR.

Characteristics

Spacecraft delta v: 1,900 m/s (6,200 ft/sec). Electric System: 0.67 average kW.

Gross mass: 970 kg (2,130 lb).
Unfuelled mass: 497 kg (1,095 lb).
Height: 1.80 m (5.90 ft).
Thrust: 26.77 kN (6,018 lbf).
Specific impulse: 293 s.
First Launch: 2002.07.03.
Number: 1 .

More... - Chronology...


Associated Countries
Associated Engines
  • Star 30 Thiokol solid rocket engine. Out of Production. Total flown included in total for Star-30A. Total impulse 136,455 kgf-sec. Motor propellant mass fraction 0.943. Isp=293s. More...

See also
  • Delta The Delta launch vehicle was America's longest-lived, most reliable, and lowest-cost space launch vehicle. Development began in 1955 and it continued in service in the 21st Century despite numerous candidate replacements. More...

Associated Launch Vehicles
  • Delta American orbital launch vehicle. The Delta launch vehicle was America's longest-lived, most reliable, and lowest-cost space launch vehicle. Delta began as Thor, a crash December 1955 program to produce an intermediate range ballistic missile using existing components, which flew thirteen months after go-ahead. Fifteen months after that, a space launch version flew, using an existing upper stage. The addition of solid rocket boosters allowed the Thor core and Able/Delta upper stages to be stretched. Costs were kept down by using first and second-stage rocket engines surplus to the Apollo program in the 1970's. Continuous introduction of new 'existing' technology over the years resulted in an incredible evolution - the payload into a geosynchronous transfer orbit increasing from 68 kg in 1962 to 3810 kg by 2002. Delta survived innumerable attempts to kill the program and replace it with 'more rationale' alternatives. By 2008 nearly 1,000 boosters had flown over a fifty-year career, and cancellation was again announced. More...
  • Delta 2 7000 American orbital launch vehicle. The Delta 7000 series used GEM-40 strap-ons with the Extra Extended Long Tank core, further upgraded with the RS-27A engine. More...
  • Delta 7425-9.5 American orbital launch vehicle. Four stage vehicle consisting of 4 x GEM-40 + 1 x EELT Thor/RS-27A + 1 x Delta K + 1 x Star 48B with 2.9 m (9.5 foot) diameter fairing) More...

Associated Manufacturers and Agencies
  • NASA American agency overseeing development of rockets and spacecraft. National Aeronautics and Space Administration, USA, USA. More...
  • APL American manufacturer of rockets and spacecraft. Applied Physics Laboratory, Johns Hopkins University, Laurel, MD, Laurel, Maryland, USA. More...

Associated Programs
  • Discovery The Discovery program was begun by NASA in the early 1990s as the planetary counterpart to the Explorer program. More...

Associated Propellants
  • Solid Solid propellants have the fuel and oxidiser embedded in a rubbery matrix. They were developed to a high degree of perfection in the United States in the 1950's and 1960's. In Russia, development was slower, due to a lack of technical leadership in the area and rail handling problems. Solid propellants have the fuel and oxidiser embedded in a rubbery matrix. They were developed to a high degree of perfection in the United States in the 1950's and 1960's. In Russia, development was slower, due to a lack of technical leadership in the area and rail handling problems. More...

Bibliography
  • McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: here.
  • CONTOUR Press Kit, Web Address when accessed: here.
  • NASA/GSFC Orbital Information Group Website, Web Address when accessed: here.
  • Space-Launcher.com, Orbital Report News Agency. Web Address when accessed: here.
  • NASA Report, CONTOUR Fact Sheet, Web Address when accessed: here.
  • NASA Report, CONTOUR Mission Overview, Web Address when accessed: here.
  • NASA Report, Comet Nucleus Tour (CONTOUR) Mishap Investigation Board Report, Web Address when accessed: here.

Associated Launch Sites
  • Cape Canaveral America's largest launch center, used for all manned launches. Today only six of the 40 launch complexes built here remain in use. Located at or near Cape Canaveral are the Kennedy Space Center on Merritt Island, used by NASA for Saturn V and Space Shuttle launches; Patrick AFB on Cape Canaveral itself, operated the US Department of Defense and handling most other launches; the commercial Spaceport Florida; the air-launched launch vehicle and missile Drop Zone off Mayport, Florida, located at 29.00 N 79.00 W, and an offshore submarine-launched ballistic missile launch area. All of these take advantage of the extensive down-range tracking facilities that once extended from the Cape, through the Caribbean, South Atlantic, and to South Africa and the Indian Ocean. More...
  • Cape Canaveral LC17A Delta launch complex. Part of a dual launch pad complex built for the Thor ballistic missile program in 1956. Pad 17A supported Thor, Delta, and Delta II launches into the 21st Century. More...

Contour Chronology


2002 July 3 - . 06:47 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17A. Launch Pad: SLC17A. LV Family: Delta. Launch Vehicle: Delta 7425-9.5. LV Configuration: Delta 7425-9.5 D292 / Star 30.
  • Contour - . Payload: Discovery 6. Mass: 1,005 kg (2,215 lb). Nation: USA. Agency: NASA; Cornell. Manufacturer: APL. Program: Discovery. Class: Comet. Type: Comet probe. Spacecraft: Contour. USAF Sat Cat: 27457 . COSPAR: 2002-034A. Apogee: 108,614 km (67,489 mi). Perigee: 212 km (131 mi). Inclination: 30.6000 deg. Period: 2,486.10 min. Launch delayed from July 1st. The latest NASA Discovery mission was successfully launched on Jul 3. The CONTOUR (Comet Nucleus Tour) probe, built and operated by the Johns Hopkins University's Applied Physics Laboratory (APL), began its five year mission to explore three comets, using repeated encounters with the earth to modify its orbit in order to reach each target. The first burn of the second stage completed at 0659 UTC putting the spacecraft in a 185 x 197 km x 29.7 deg parking orbit. At 0746 UTC the second stage restarted for a short 4s burn to 185 x 309 km x 29.7 deg, and then separated once the PAM-D (ATK Star 48B) solid third stage was spun up. The 1.5 minute burn of the third stage motor at 0748 UTC put it and CONTOUR in a 90 x 106689 km x 30.5 deg phasing orbit. By July 8 CONTOUR's orbit was 214 x 106686 km x 29.8 deg. CONTOUR stayed in this phasing orbit until August 15, when it was injected into solar orbit using its internal ATK Star 30 solid motor. Flyby of the first target, comet 2P/Encke, was scheduled for Nov 2003.

2002 August 15 - .
  • Contour Injection Maneuver To Leave Earth's Orbit - . Nation: USA. Spacecraft: Contour.

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