Orbital mechanics question DSCOVER L1 orbit

I'd imagine that one has to be travelling pretty slow to get captured in
fact. Its not like a little well one can fall into, its more like a shallow
saucer of gravity.
In relation to posting here, I think most other groups are moderated and
hence the immediacy of it is not there.
There does really need to be another group of unmoderated general space
stuff.
Brian

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From the Sofa of Brian Gaff Reply address is active
"Snidely" wrote in message
news:mn.60b07df2448f18a8.127094@snitoo...
Just this Wednesday, JF Mezei explained that ...
SpaceX is about to launch a NOAA satellite to L1 between earth and sun.

Appears the launch window is very small (no 5 minute leaways on eaither
end of prefered launch time), and that today is last possible launch
date since the moon would prevent launch later on.


How does such a launch work ? Obviously, they launch at Cape's orbital
inclination. Do they correct it to equatorial 0° inclination prior to
MECO ? Or do they correct to an inclination that would be between tro]ic
of capricorn and equator to be directrly below sun ? (and in such a
case, can they launch south east or are they restricted to north-east
like shuttle ?

Does the vehicle first enter earth orbit conventionally and then uses
second/thirst stages to raise orbit progressively until it is at the
million mile distance at which point the L2 forces kick in and grab the
vehicle into a stationary position relative to axis between earth and sun
?

Or does the vehicle shoot straight up (more or less) to reach that L1
point where it no longer has to worry about orbital speed because
gravity on both sides keep the vehicle stationary relative to earth/sun ?

(seems odd to post this in dot-station, since it isn't going to the
station and there is launch discussion in dot-policy)

I don't have the full answer, but note this from the AP report:

"DSCOVR will spend nearly four months traveling 1 million miles, four
times farther than the moon, to the so-called Lagrange point, a
gravity-neutral position in direct line with the sun. "

URL:
http://seattletimes.com/html/businesstechnology/2025669167_apxscideepspaceobservatory.html

The 2 main ways of going deep a

1) Apollo-style, where a big "top stage" provides a lot of boost
short-term, and that boost is applied from LEO. (The last Russian Mars
mission ended at this point, apparently due to booster issues.) Expect a
transfer orbit; something like a Hohmann orbit would be the low-cost (and
slow) way to get there.

2) Ion-engine, SMART-1 style: low-thrust over a long period of time. The
orbit will be very different for this; I haven't seen too many diagrams.
SMART-1 did a "spiral" lasting about a month, if memory and a quick scan
of the wikicle serve.
URL:http://en.wikipedia.org/wiki/SMART-1
Going 4 times farther in 3 times the travel time seems reasonable.

The NOAA press kit doesn't say anything about an ion engine, so they may
be using the restartable Falcon upper stage the way Apollo used the SIV-B.

URL:http://www.nesdis.noaa.gov/DSCOVR/press.html


Ah, looks like I'm right:

quote
At T+30 minutes and 9 seconds, the MVac engine re-ignited for a burn of 58
seconds to boost the stack into an L1 Transfer Orbit. DSCOVR was targeting
an insertion orbit of 187 by 1,241,000 Kilometers inclined 37 degrees
which will be modified through propulsive maneuvers by the spacecraft to
reach the L1 point 1.5 Million Kilometers from Earth for orbital
insertion. The achieved insertion orbit was 187 by 1,371,145 Kilometers at
an inclination of 37.09° marking a very precise insertion with a minute
overperformance of just a handful m/s.
/quote
URL:http://www.spaceflight101.com/dscovr-mission-updates.html
[scroll down more than 1/3 page past the picture of the 2nd stage engine
aglow]

HTH.

/dps "still some fu for my goo"

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Ieri, oggi, domani