FREQUENTLY ASKED QUESTIONS
General information about Lunar Prospector
- What powers Prospector?
- How big is Prospector?
- What is unique about Prospector compared to previous lunar missions?
- What will Prospector tell us?
- Will Lunar Prospector land on the Moon?
- How long will Prospector take to get to the Moon?
- Who built the spacecraft?
- How old is the Moon?
- How far is the Moon from the Earth?
- What are some of the physical differences between the Earth and the Moon (size, mass)?
- Why do we only see one face of the Moon?
- Why are the Moon's magnetic fields so unique (no dipole field)?
- Why is there no atmosphere on the Moon?
- What is a blue Moon?
- How many times has NASA been to the Moon?
- Why hasn't NASA been back to the Moon since Apollo?
- Why should we go back to the Moon now?
- Why do we suspect there might be water on the Moon?
- Why don't we already know about water on the Moon?
- Why is finding water on the Moon significant?
- What does "spin-stabilized" mean?
- How was Prospector's launch date determined?
- What does the primary mission mean?
- How will the spacecraft get to orbit (what is the launch vehicle)?
- What are you prospecting for? Are you looking for gold and silver?
- Will you be bringing material back from the Moon?
- What will happen to Prospector after a year?
- What will the extended mission tell us?
- What is required to achieve lunar orbit?
- How fast will the spacecraft move around the Moon?
- How far above the Moon does the spacecraft orbit?
- How does the spacecraft get power when it can't see the Sun?
- What kind of computer runs the spacecraft?
- Will Lunar Prospector see the Apollo landing sites?
- Why will Prospector be in a polar orbit?
- When and how will the data be transmitted and received?
- What is outgassing (an outgassing event)?
- What is a spectrometer?
- How will the masts deploy?
- What is Discovery?
- What are the booms (masts) for?
- Why doesn't Prospector have a camera?
- How will the mission end?
- What did the mission cost?
- What frequency will the spacecraft transmit on
What powers Prospector?
Lunar Prospector is run by rechargeable, solar-powered nickel-hydrogen batteries.
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How big is Prospector?
The spacecraft is shaped like a drum, 4.25 feet (1.3 meters) -high, with
a diameter of 4.5 feet (1.4 meters). When full of fuel, Prospector weighs
650 pounds (295 kilograms). The three masts are each 8 feet (2.4 meters)
-long.
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What is unique about Prospector compared to previous
lunar missions?
The Apollo missions only mapped about 25 percent of the lunar surface,
around the Moon's equator. Prospector will map the entire lunar surface
for the first time. Additionally, Prospector will be much less expensive,
and carry fewer experiments, than the Apollo missions. It is NASA's third
Discovery mission and the first competitively selected Discovery mission.
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What will Prospector tell us?
Lunar Prospector will address many of the unanswered questions about the
Moon's resources, origin and structure that have been posed by NASA's
Lunar Exploration Science Working Group (LExSWG). This data could help
scientists plan a potential lunar base and develop theories of the formation
of the Moon, Earth and Solar System.
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Will Lunar Prospector land on the Moon?
No. Prospector is an orbiter, not a lander, and will obtain all its data
remotely.
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How long will Prospector take to get to the Moon?
Lunar Prospector's flight time to the Moon was 105 hours. It was launched
on January 6, 1998, and arrived at the Moon (entered lunar orbit) on January
11, 1998.
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Who built the spacecraft?
The spacecraft was built by Lockheed Martin Missiles & Space of Sunnyvale,
California.
How old is the Moon?
Moon rock samples brought to Earth by the Apollo missions have been dated to between 3 and 4.6 billion years old. The Earth is 4.5 to 4.6 billion years old, but the oldest known Earth rocks are less than 4 billion years old, and rocks older than 3 billion years are rare.
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How far is the Moon from the Earth?
On average, the Moon is 240,250 miles (384,400 km) from the Earth. At
the Moon's perigee (its closest approach to Earth in its elliptical orbit),
it is 227,063 miles (363,300 km) away. At its apogee (the farthest distance
away), the Moon is 253,438 miles (405,500 km) from the Earth. It circles
the Earth with a mean orbital velocity of 2,300 miles per hour (3,680
km per hour).
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What are some of the physical differences between
the Earth and the Moon (size, mass)?
|
Earth |
Moon |
|
|---|---|---|
| Mass (1024kg) | 5.9736 |
0.07349 |
| Volume(1010 km3) | 108.321 |
2.1973 |
| Mean radius(km) | 6371 |
1737.5 |
| Mean density(9 kg/m3) | 5520 |
3340 |
| Surface gravity(m/s2) | 9.78 |
1.62 |
| Escape velocity(km/s) | 11.2 |
2.38 |
Why do we only see one face of the Moon?
The Moon rotates once around its axis in the same amount of time it completes a full orbit of the Earth. In other words, the Moon's rotational period and its orbital period are equal. This is called synchronous rotation.
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Why are the Moon's magnetic fields so unique
(no dipole field)?
The Moon has no global magnetic field. But some of its surface rocks exhibit
remnant magnetism, indicating that there may have been a global magnetic
field early in the Moon's history. One of the questions Lunar Prospector
will address is whether an airless celestial body (like the Moon) can
acquire magnetic features from impacts, such as asteroids and comets.
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Why is there no atmosphere on the Moon?
Basically, because it is too tiny. The Moon does not have a strong enough
gravitational field to support an atmosphere.
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What is a blue Moon?
A second full Moon in one month is called a blue Moon.
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How many times has NASA been to the Moon?
NASA has sent 22 missions to the Moon, between 1964 and 1972. NASA has
had six successful human landings on the Moon, preceded by two orbiters
with humans aboard.
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Why hasn't NASA been back to the Moon since Apollo?
NASA funding decreased after the Apollo missions, and scientists wanted
to explore aspects of the Solar System other than the Moon.
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Why should we go back to the Moon now?
Much of the Moon remains a mystery. Data collected by the Apollo missions
focused on a narrow band around the Moon's equator, mapping only 25 percent
of the lunar surface. Prospector will fill in the gaps.
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Why do we suspect there might be water on the
Moon?
Although we know that the Moon does not have any water of its own, the
Moon has been bombarded by comets -- mixtures of dust and ice -- for billions
of years. Any ice deposited on the lunar surface in the Moon's thin atmosphere
and bathed in warm sunlight would likely evaporate. However, ice deposits
would be unlikely to melt in very cold craters near the Moon's south pole,
where the Sun never shines. We expect, if we find water on the Moon, that
it will be frozen in soil deep in these craters.
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Why don't we already know about water on the
Moon?
Although the Apollo program returned vast amounts of lunar data to Earth,
those missions only studied equatorial regions of the Moon. Apollo found
no evidence of ice or water in those areas, and scientists suspect that
the Moon's surface is too warm near the equator to keep ice from evaporating
and exiting the thin atmosphere. However, deep, dark craters at the lunar
poles are very cold, and could be home to frozen water deposited by comets
over billions of years.
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Why is finding water on the Moon significant?
The discovery of water ice on the Moon would be a vital step toward the
building of a human outpost on the Moon. According to NASA's February
1996 Strategic Plan, goals of NASA's Human Exploration and Development
of Space Enterprise (HEDS) include the following: "Explore and settle
the Solar System. Achieve routine space travel. Enrich life on Earth through
people living and working in space." In the Strategic Plan, HEDS
indicates the necessity for missions that will "demonstrate the feasibility
of utilizing local resources to 'live off the land,'" in order to
meet its goals. Water is an extremely expensive material to transport
to the Moon. If Lunar Prospector discovers water ice on the Moon, a very
important local resource will be available to astronauts because we use
water to drink, to bathe and to fuel spacecraft (after splitting water
molecules into their individual elemental components, hydrogen and oxygen).
What does "spin-stabilized" mean?
The Lunar Prospector spacecraft rotates around its own up-and-down axis, spinning like a top. Such "spin-stabilization" keeps the spacecraft's orientation in space under control. Prospector's engineer's designed the spacecraft to have a short and fat shape (as opposed to a long and narrow one), so that an active damper isn't required to control wobbling.
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How was Prospector's launch date determined?
In planning a trip to the Moon, the two most important issues are power
and propellant. Lunar Prospector could have been launched to the Moon
on any day (in fact, two times a day -- see below), however only on those
days in which the spacecraft pointing and orbit insertion velocity constraints
are possible candidates. Firstly, to generate sufficient electrical power
to run the spacecraft, the solar array (solar panels) must be properly
pointed to "see" the Sun. Secondly, arrival at the Moon must
correspond to the time when the least amount of propellant is needed to
fire the jets and thus establish lunar orbit. Together, both of these
constraints limit the launch opportunity to only a few days each month.
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What does the primary mission mean?
During its first year in orbit, Lunar Prospector will conduct its primary
mission. All five instruments will collect data as the spacecraft orbits
at an altitude of 63 miles (100 km) above the surface of the Moon.
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How will the spacecraft get to orbit (what is
the launch vehicle)?
The launch vehicle is a three-stage, solid fuel Lockheed Martin Athena
II rocket.
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What are you prospecting for? Are you looking
for gold and silver?
We are not prospecting for gold and silver. We are looking for resources
(such as water) in addition to certain elements (such as hydrogen, helium,
and iron) that would be very important to build and maintain a Solar System
"launchpad" and, perhaps, to eventually establish a lunar colony.
Other useful resources Lunar Prospector will search for are gases such
as nitrogen and carbon dioxide.
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Will you be bringing material back from the Moon?
No. Prospector will orbit the Moon. Since the spacecraft will not land
on the Moon, and it will not return to Earth, it will not bring any lunar
samples back to Earth. It will, however, transmit vast amounts of data
to Earth before it impacts on the Moon's surface at the end of the mission.
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What will happen to Prospector after a year?
Prospector will begin an extended mission after its initial one-year primary
mission. During the extended period (after approximately another six months),
the mission will end when the spacecraft runs out of fuel. It will then
impact the surface of the Moon.
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What will the extended mission tell us?
After one year, we expect to have enough fuel left for Prospector to drop
down to an elliptical orbit with a minimum altitude of 6 miles (10 km).
All five instruments will continue to function. The extended mission will
enable us to obtain data with much better resolution, since the spacecraft
will be in orbit longer, and Prospector will be closer to the surface.
Some of the instruments provide better data over a longer period of time,
and others do so at closer distances.
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What is required to achieve lunar orbit?
Lunar Prospector was launched from Pad 46 of Spaceport Florida (Cape Canaveral,
Florida) aboard a Lockheed Martin Athena II three-stage rocket. As with
all other space missions, the spacecraft was first launched into a low
Earth orbit, called a "parking orbit." After circling in this
orbit halfway around the Earth, the Trans Lunar Injection Stage (kick
motor) of the launch rocket fired, propelling Prospector toward the Moon.
After four days of coasting to the Moon, Prospector arrived at a distance
55 miles from the Moon. At that point, the spacecraft's thrusters (engines)
fired in order to slow the vehicle down and settle it into its final lunar
orbiting pattern, circling at 63 miles above the surface of the Moon.
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How fast will the spacecraft move around the
Moon?
Prospector will have an orbital velocity of 5,868 km per hour (3,668 miles
per hour). It will circle the Moon once every 118 minutes.
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How far above the Moon does the spacecraft orbit?
Prospector will map the Moon from a 63-mile (100-km) altitude orbit during
the one-year primary mission. If the spacecraft continues into an extended
mission (most likely for six months after the primary mission), it will
swing down to a 6-mile (10-km) altitude.
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How does the spacecraft get power when it can't
see the Sun?
A rechargeable battery will power Lunar Prospector while it is on the
dark side of the Moon. Each time it reappears in the Sun, it will recharge.
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What kind of computer runs the spacecraft?
There is no computer on board the spacecraft. A simple electronics box,
called the Command and Data Handling Unit, accepts a maximum of 60 commands
from Earth. Lunar Prospector is controlled by a ground computer at NASA
Ames Research Center in Mountain View, California (San Franscisco Bay
Area).
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Will Lunar Prospector see the Apollo landing
sites?
Lunar Prospector will "see" the entire surface of the Moon.
Although the spacecraft does not carry a camera, it will conduct data
measurements over the entire lunar surface.
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Why will Prospector be in a polar orbit?
Lunar Prospector will be in a polar orbit because we want to map the entire
surface of the Moon. Prospector will circle the Moon, crossing both the
north and south poles, while the Moon spins on its north/south pole-axis.
As the spacecraft completes circle after circle, the Moon has rotated,
and all surfaces of the Moon will eventually be mapped.
When and how will the data be transmitted and received?
Lunar Prospector has two antennae, an omni antenna and a medium-gain antenna. Both sit on top of the spacecraft (the omni sits above the medium-gain). The omni antenna will be used for up-linking commands (en route to the Moon), and the medium-gain antenna will be used while the spacecraft is in lunar orbit, to down-link data to the Earth. An S-band transmitter and an S-band receiver will communicate information between Prospector and the Earth via NASA's Deep Space Network.
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What is outgassing (an outgassing event)?
Outgassing is the venting of gases from the lunar interior.
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What is a spectrometer?
A spectrometer is an instrument that detects incoming information (say,
light or matter) and disperses (scatters) it, organizing it according
to energy or mass. One kind of spectrometer is a prism -- it receives
light and spreads that light out into its individual wavelengths (which
appear as the colors of the rainbow).
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How will the masts deploy?
The booms deploy very much like springs unwinding. When mission controllers
provided the command to do so, a small device called a "pyrotechnic
actuator" ignited, melting a paraffin seal which released the booms
to slowly unwind in space.
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What is Discovery?
Discovery is NASA's new program for developing missions that return the
best science per dollar spent. The missions, which are by definition "Faster,
Better, and Cheaper," must follow strict, streamlined development
timelines and are required to adhere to a maximum budgetary constraint
of $150 million (1992 dollars) for development. Discovery encourages private
corporations, individuals and universities to work cooperatively with
the federal government. NASA issues an Announcement of Opportunity to
call for proposals from prospective mission designers.
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What are the booms (masts) for?
The booms isolate the instruments from the body of the spacecraft.
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Why doesn't Prospector have a camera?
Prospector can't do everything, and the Moon has already been extensively
photographed by previous missions. As a Discovery mission, Prospector
has a small payload of five instruments that focus on a narrow goal --
not every experiment can be chosen. Non-Discovery missions carry multi-discipline
payloads of many more experiments, and consequently cost much more money.
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How will the mission end?
When Prospector's fuel runs out, scientists will not be able to make orbital
corrections and the spacecraft will impact the surface of the Moon.
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What did the mission cost?
Mission development cost about $34 million, which excludes the launch
vehicle (~$25 million) and the cost of operations (~$4 million). The total
cost was $63 million.
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What frequency will the spacecraft transmit on?
The downlink frequency is 2273.000 MHz and the uplink frequency is 2093.0541
Mhz. Transmissions from the spacecraft to NASA's Deep Space Network on
Earth will be on the down-link frequency and commands to the spacecraft
from the Earth will be on the up-link frequency.
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