If we do return to the Moon

Steen Eiler Jørgensen wrote:
Dholmes wrote:


What did I miss in my quick list?


Development of a communications relay satellite in a halo orbit around the
L2 Lagrange point in the Earth-Moon-system, providing a communications link
to the far side of the Moon.

From http://www.tsgc.utexas.edu/archive/design/farside.html

"During the construction phase, a satellite in an L2 halo orbit will relay
data from the lunar surface to a geostationary satellite in Earth orbit to
the Earth's surface. When the base becomes fully operational, however, a
radio-free sky is desired to take accurate astronomical readings. Therefore,
a fiber optic cable will be used as a communication link from the base to a
transmitter/receiver station on the near side of the Moon. It will be laid
out by a robotic rover from the base to the limb of the Moon. From there,
the signal can be broadcasted directly to Earth without interfering with
astronomical observations."

From http://www.tsgc.utexas.edu/archive/design/farside2.html

Sounds like a good idea to me. This is also the proposed location for
the James Webb space telescope:
http://www.space.com/businesstechnol...st_030108.html


--
Hop David
http://clowder.net/hop/index.html

Hop David wrote:

Sounds like a good idea to me. This is also the proposed location for
the James Webb space telescope:

One should be careful using a term like "L2". There is an important
distinction between which system "L2" refers to. The JWST is to be parked in
L2 in the Sun-Earth-system (in orbit around the Sun, 1.5 million km farther
out than the Earth, but with the same angular velocity around the Sun as the
Earth), while the LUFASIRS (homemade NASA acronym for Lunar Far Side Relay
Satellite :-) ) will be in orbit around L2 in the Earth-Moon-system (in
orbit around the Earth, somewhat farther out than the Moon, but with the
same angular velocity around the Earth as the Moon).

A comms relay satellite at L2 in the Sun-Earth-system would only be able to
support comms from the far side of the Moon half of its 29,5 days synodic
period.

Another important distinction between the JWST and the LUFASIRS is that
while the JWST can probably be "parked" fairly close to the L2 (depending on
how many spacecraft are already out there), the LUFASIRS must orbit this
point at a considerable distance, as to prevent the Moon from blocking the
satellite's view of Earth.

--
Steen Eiler Jørgensen
"Time has resumed its shape. All is as it was before.
Many such journeys are possible. Let me be your gateway."

Steen Eiler Jørgensen wrote:
Hop David wrote:


Sounds like a good idea to me. This is also the proposed location for
the James Webb space telescope:


One should be careful using a term like "L2". There is an important
distinction between which system "L2" refers to. The JWST is to be parked in
L2 in the Sun-Earth-system (in orbit around the Sun, 1.5 million km farther
out than the Earth, but with the same angular velocity around the Sun as the
Earth), while the LUFASIRS (homemade NASA acronym for Lunar Far Side Relay
Satellite :-) ) will be in orbit around L2 in the Earth-Moon-system (in
orbit around the Earth, somewhat farther out than the Moon, but with the
same angular velocity around the Earth as the Moon).

Of course it's obvious you meant the earth-moon L2 and not the earth-sun
L2. I didn't have my thinking cap on this morning.


A comms relay satellite at L2 in the Sun-Earth-system would only be able to
support comms from the far side of the Moon half of its 29,5 days synodic
period.

Another important distinction between the JWST and the LUFASIRS is that
while the JWST can probably be "parked" fairly close to the L2 (depending on
how many spacecraft are already out there),

IIRC correctly they also wanted a halo for the JWST that would keep a
minimum angular separation between earth and sun. I guess it's not good
to point your communication dish in a near sunward direction.

the LUFASIRS must orbit this
point at a considerable distance, as to prevent the Moon from blocking the
satellite's view of Earth.





--
Hop David
http://clowder.net/hop/index.html

In article ,
Hop David wrote:
IIRC correctly they also wanted a halo for the JWST that would keep a
minimum angular separation between earth and sun. I guess it's not good
to point your communication dish in a near sunward direction.

The usual problem is not damage to the hardware -- even if you're using a
solid dish rather than a mesh one, problems with focusing of sunlight can
be limited by choosing a suitable paint -- but added noise in the
receivers from having the Sun in the background.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

In article ,
Steen Eiler Jørgensen wrote:
"During the construction phase, a satellite in an L2 halo orbit will relay
data from the lunar surface to a geostationary satellite in Earth orbit to
the Earth's surface. When the base becomes fully operational, however, a
radio-free sky is desired to take accurate astronomical readings. Therefore,
a fiber optic cable will be used..."

Fiber optics unfortunately can't give you mobile communications. The
solution to the "radio-free sky" problem was figured out quite a while
back: farside communications gear is built to use two different radio
bands, and they are used in rotation on a predetermined schedule, so each
band is quiet half the time.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

"Steen Eiler Jørgensen" wrote in message
. ..
Dholmes wrote:

What did I miss in my quick list?

Development of a communications relay satellite in a halo orbit around the
L2 Lagrange point in the Earth-Moon-system, providing a communications
link
to the far side of the Moon.


A communication link
"Project ECHO: Electronic Communications from Halo Orbit - Abstract: The
design of a communications relay to provide constant access between the
Earth and the far side of the Moon is presented. Placement of the relay in
a
halo orbit about the L2 Earth-Moon Lagrange point allows the satellite to
maintain constant simultaneous communication between Earth and scientific
payloads on the far side of the Moon. The requirements of NASA's
Discovery-class missions adopted and modified for this design a total
project cost should not exceed $150 million excluding launch costs, launch
must be provided by Delta-class vehicle, and the satellite should maintain
an operational lifetime of 10 to 15 years. The spacecraft will follow a
transfer trajectory to the L2 point, after launch by a Delta II 7925
vehicle
in 1999. Low-level thrust is used for injection into a stationkeeping-free
halo orbit once the spacecraft reaches the L2 point. The shape of this
halo
orbit is highly elliptical with the maximum excursion from the L2 point
being 35000 km. A spun section and despun section connected through a
bearing and power transfer assembly (BAPTA) compose the structure of the
spacecraft. Communications equipment is placed on the despun section to
provide for a stationary dual parabolic offset-feed array antenna system.
The dual system is necessary to provide communications coverage during
portions of maximum excursion on the halo orbit. Transmissions to the NASA
Deep Space Network 34 m antenna include six channels (color video, two
voice, scientific data from lunar payloads, satellite housekeeping and
telemetry and uplinked commands) using the S- and X-bands. Four
radioisotope
thermoelectric generators (RTG's) provide a total of 1360 W to power
onboard
systems and any two of the four Hughes 13 cm ion thrusters at once. Output
of the ion thrusters is approximately 17.8 mN each with xenon as the
propellant. Presence of torques generated by solar pressure on the antenna
dish require the addition of a 'skirt' extending from the spun section of
the satellite for balance. Total mass of the satellite is approximately
900
kg at a cost of $130 million FY99."


Reasonable price as well.

Dholmes wrote:
what do we need to do before we send men back ?

A couple of things I came up with a

An orbiter to map the Moon in detail especially the poles. Many areas of the
Moon today are not mapped to 20 m resolution we can easily do 10m for the
entire moon and 1-2m for selected portions.

A follow on to Prospector getting a better idea of where the hydrogen is.

I am hoping ESA's SMART-1 will give helpful information:
http://sci.esa.int/science-e/www/are...cfm?fareaid=10


A radar map to give us a picture at depth of the Moons surface.

A couple of landers at potential base sites would be usefull.

What did I miss in my quick list?







--
Hop David
http://clowder.net/hop/index.html

"Hop David" wrote in message
...


Dholmes wrote:
what do we need to do before we send men back ?

A couple of things I came up with a

An orbiter to map the Moon in detail especially the poles. Many areas of
the
Moon today are not mapped to 20 m resolution we can easily do 10m for
the
entire moon and 1-2m for selected portions.

A follow on to Prospector getting a better idea of where the hydrogen
is.

I am hoping ESA's SMART-1 will give helpful information:
http://sci.esa.int/science-e/www/are...cfm?fareaid=10


Not a big fan of SMART-1 Japan's Selene and Lunar A interest me more.
Selene IMO sounds like a great probe:

http://moon.nasda.go.jp/en/selene/outline/inst.html

Dholmes wrote:
"Hop David" wrote in message
...


Dholmes wrote:

what do we need to do before we send men back ?

A couple of things I came up with a

An orbiter to map the Moon in detail especially the poles. Many areas of

the

Moon today are not mapped to 20 m resolution we can easily do 10m for

the

entire moon and 1-2m for selected portions.

A follow on to Prospector getting a better idea of where the hydrogen

is.

I am hoping ESA's SMART-1 will give helpful information:
http://sci.esa.int/science-e/www/are...cfm?fareaid=10



Not a big fan of SMART-1 Japan's Selene and Lunar A interest me more.
Selene IMO sounds like a great probe:

http://moon.nasda.go.jp/en/selene/outline/inst.html



Is there a launch date set for Selene?

--
Hop David
http://clowder.net/hop/index.html

A return to the Moon is the first step in going to Mars with people. You can
skip this step, but its not advisable. The Moon is closer and access to Earth
is continuous. If something were to go wrong on the Moon, it would be easier to
Abort to Earth than it would be to abort to Earth from Mars. One can build
nuclear rockets to get to the Moon, and those same nuclear rockets can be used
for a mission to Mars. it is not necessary to grow food on the Moon in order to
have a mission there. The outbound and inbound journey is a matter of days.
With a mission to Mars, you commit yourself to years in space and past a
certain point their is no turning back. The same principles in Mars direct can
be applied to the Moon. You can land an Earth return vehicle on the Moon before
astronauts arrive. You make sure all systems are nominal before you send the
astronauts. On site fuel processing is not required. The Earth return vehicle
can bring its own fuel with it. You can land the ERV just before lunar night,
that will keep the liquid hydrogen nice and cold for 2 weeks, minimizing
boil-off. The crew arrives just in time for Lunar dawn, do their mission and
return to Earth on the ERV.

Tom