SELENE mission

[3488]

Selene / Kaguya.<br /><br />Post launch self portraits.<br /><br />Kaguya self-portrait: High-gain antenna.<br /> About eight hours after launch, Kaguya deployed its high-gain antenna and solar paddle. <br />A few hours later, the spacecraft took a photo to document the position of <br />the antenna using its onboard camera. Credit: JAXA.<br /><br />Kaguya self-portrait: Solar paddle.<br />About eight hours after launch, Kaguya deployed its high-gain antenna and solar <br />paddle. A few hours later, the spacecraft took a photo to document the position of<br />the paddle using its onboard camera. The triangle shape visible in the image <br />is a truss that supports the paddle, which is extremely foreshortened from this point <br />of view. Credit: JAXA.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[rocketscientist327]

Wife is Japanese, and I get more offended than she does. LOL However, from his broken english he may just not understand that.<br /><br />VR<br />Rocket Scientist

 

[l3p3r]

Hi 3488!!<br />Could you please explain the term "apolune reduction" to me, quick google didn't return anything <img src="/images/icons/smile.gif" /><br />cheers!<br /> <div class="Discussion_UserSignature"> </div>

 

[3488]

Hi 13p3r.<br /><br />Apolune is the furthest point in an orbit around the Moon (Perilune the closest point).<br /><br />The Apolune Reduction, means that SELENE, will reduce its highest point in lunar orbit so <br />it becomes more circular.<br /><br />SELENE, will not enter into a circular orbit when it arrives, so several <br />thrustings over many orbits are required to reduce the Apolune.<br /><br />In short, its making a highly elliptical orbit into a more circular one, without reducing its<br />Perilune (closest distance from the Moon).<br /><br />Hope that helps.<br /><br />AFAIK, Apolune & Perilune are not 'official terms' but I have seen them used <br />several times before.<br /><br />Also there is Perijove & Apojove (Closest & furthest points in an orbit around Jupiter).<br />& have seen Periherm & Apoherm closest & furthest points in an orbit around Mercury).<br /><br />I do not know what they are for the other planets.<br /><br />Obviously we know what Perigee, Apogee, Perihelion & Aphelion are.<br /><br />General terms are usually Periapsis & Apoapsis, which can be used for any object.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[l3p3r]

thanks very much! <br />I wasn't sure if the term implied another mechanism for reducing the apoapsis (rather than thrusters) or not <img src="/images/icons/smile.gif" /> <br /><br />One other thing, is the term 'apocynthion' still applicable to the furthest point in an orbit from the moon? (as per wiki ) <br /><br />edit: yeah there are so many of these things it gets very confusing! i've always used aphelion and perihelion as general terms but now i see 'apoapsis' and 'periapsis' are correct =) <div class="Discussion_UserSignature"> </div>

 

[3488]

Apocynthion (used during the Lunar orbiters & Apollo) AFAIK has been replaced with Apolune.<br /><br />I think wiki has not followed up that fact. I am very certain, that it is Apolune. I think<br />wiki needs updating / correcting.<br /><br />WOW. The other planets are on there.<br /><br />List below.<br /><br />Perihelion - Aphelion = Sun.<br /><br />Periherm - Apoherm = Mercury.<br />Pericytherion - Apocytherion = Venus,<br />Perigee - Apogee = Earth,<br />Perilune - Apolune = Moon,<br />Periareion - Apoareion = Mars, <br />Perijove - Apojove = Jupiter,<br />Perikrone - Apokrone = Saturn, <br />Periuranion - Apouranion = Uranus, <br />Periposeidion - Apoposeidon = Neptune,<br />Perihadion - Apohadion = Pluto. <br /><br />I wonder about Eris, 1 Ceres, etc <img src="/images/icons/crazy.gif" /> ?<br /><br />Periastron - Apoastron = A star that is not the Sun.<br /><br />Thanks.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[l3p3r]

If I could only find a reference for aplune et al. I'd change the wiki page <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

 

[3488]

Thank you very much, a most interesting exchange. Often wondered what the terms were for<br />the others. <br /><br />I had almost figured out what the terms might be for Venus, Mars, Saturn & <br />Neptune, but was not sure.<br /><br />Uranus was a real stumper!!! <img src="/images/icons/laugh.gif" /><br /><br />My questions answered.<br /><br />Thank you very much.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[astrowikizhang]

"Apolune is the furthest point in an orbit around the Moon (Perilune the closest point). "<br /><br />I used to use the term "Apogee" and "Perigee". They are on opposite ends of longest axis of the elliptical orbit. If I am correct, the thrusters are fired at perigee so that height on apogee is reduced.

 

[3488]

Perigee & Apogee AFAIK relate only to orbits to the Earth?????<br /><br />Yes, the thrusters are fired at Perilune, to reduce the rate of recession, so the next <br />Apolune will be lower.<br /><br />Cool self portraits from SELENE / Kaguya.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[alokmohan]

You are correct I shall not use in future.

 

[astrowikizhang]

"Perigee & Apogee AFAIK relate only to orbits to the Earth?????"<br /><br />Think you are right, should not use these terms on moon. <br /><br />More from Apollo Flight Journal:<br /><br />http://history.nasa.gov/ap15fj/09day4_lunar_encounter.htm <br /><br />[Readers should note that there are a wide variety of terms used to describe the high and low points in a lunar orbit. For example "aposelene" and "periselene" respectively are commonly seen. Strictly speaking, there are four terms used by the people of Apollo. If a spacecraft has been launched from Earth then the terms "apocynthion" and "pericynthion" should be used. "Apolune" and "perilune" are intended for describing the orbits of spacecraft that have been launched from the Moon.]

 

[l3p3r]

wow! talk about a whole new level of confusion! <img src="/images/icons/tongue.gif" /> <br /><br />so now we have different terms for being in orbit around the moon based on where you started from... i think i'll just stick with apoapsis and periapsis <img src="/images/icons/smile.gif" /> <br /><br />thanks for the info and especially for that source! <div class="Discussion_UserSignature"> </div>

 

[hiro2002]

>>SELENE, will not enter into a circular orbit when it >>arrives, so several <br /> />>thrustings over many orbits are required to reduce >>the Apolune. <br /><br />While reducing the Apolune, Kaguya(SELENE) will release "Relay satellite" and "VRAD satellite".<br /><br />http://www.jaxa.jp/countdown/f13/overview_kaguya_e.html<br />

 

[astrowikizhang]

Does JAXA use the Deep Space Network to track their spacescrafts? Or they have their own boats and airplanes to receive the telemetry?

 

[hiro2002]

JAXA uses them.http://track.sfo.jaxa.jp/en/contents/facilities.html<br /><br />and NASA's Deep Space Network.<br /><br />

 

[astrowikizhang]

After the Period Error Correction Maneuver on Sept 21, SELENE's orbit is:<br /><br />Apogee altitude 379,196 km<br />Perigee altitude 1,055 km<br />Period 10 days 0 hours 48 minutes<br /><br />Seems it is on the 2nd round and closing to LOI.

 

[alokmohan]

Has SELENE arrived?If not what is its expected date of arrival?

 

[astrowikizhang]

Instead of an Apollo-style TLI, recent moon orbiters use several burns on elliptic orbits, generally raise the apogee before Lunar Orbit Injection, which seems requiring less energy but more days to arrive moon orbit. <br /><br />Why does this use less energy? Does the earth help accelerating when it gets around? Will this method be useful on future manned moon missions?

 

[no_way]

http://en.wikipedia.org/wiki/Low_energy_transfers

 

[astrowikizhang]

Seems the low energy transfers stand for the Weak Stability Boundary transfers, which taking the spacecraft to the region of Lagrangian points of the Earth-Sun system (L2?), then a small manoeuver will lead it the the moon. This approach was first demonstrated by JAXA's Hiten mission. Need months to arrive.<br /><br />Recent moon orbiters from Japan, China, and India use transfer via GTO/EPO. It is a different approach, spacecrafts are placed on a highly elliptic parking orbit by the launch vehicle, then transfer to the lunar orbit using on-board thrusters. A journey like this takes weeks. <br /><br />http://www.ias.ac.in/jessci/dec2005/ilc-15.pdf

 

[mithridates]

It arrives on October 4th, so that's nine days. Unless you were talking about the date of the final orbit correction. <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[MeteorWayne]

It should be pointed out that for the Apollo missions, the purpose was to get there and back as quickly as possibe, to reduce the amount of time when a critical failure could occur, as well as limiting the astronauts exposure to radiation and micrometeoroids (which were less well known back then).<br /><br />With an unmanned satellite, you try and do it as weight efficiently as possible (the more you save on propellant ( <img src="/images/icons/wink.gif" /> s_g) the more weight that you have for science. So it makes sense to take your time if the benefit/cost ratio says a longer trip gives you more science with a minimal increase of risk. <br /><br />MW <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[no_way]

<blockquote><font class="small">In reply to:</font><hr /><p>So it makes sense to take your time if the benefit/cost ratio says a longer trip gives you more science with a minimal increase of risk.<p><hr /></p></p></blockquote><br />.. although with Japanese / JAXAs extremely bad luck with solar flares so far ( 2002 - Nozomi , 2003 - ADEOS/Midori 2 and DRTS/Kodama ) they might want to hurry up .. <br /><br />EDIT: Forgot to knock on wood

 

[MeteorWayne]

The sun is EXTREMELY quiet right now, just got finished with SOHO and Spaceweather links. We are at the nadir of the cycle. The surface of the sun is almost featureless, although one sees on the C2 and C3 images the hint that something very active is about to rotate into view, and fairly close (35dN? ) to the equator. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>