baalke@mars.jpl.nasa.gov (Ron Baalke) (11/11/90)
CRAF/Cassini Status Report November 9, 1990 The good news concerning the CRAF/Cassini mission, is that it looks like both missions will be funded. Congress approved both missions earlier in the year, but during the recent budget negotiations, it looked like that the CRAF portion was not going to be funded. The total budget for both missions is 1.6 billion dollars, with 145 million needed in the 1991 fiscal year budget to get the projects started. Only 95 million was approved - being 50 million short, things were looking grim for the CRAF mission, as the Cassini mission has priority. However, most of the 50 million has since been restored which should enable the start of both the CRAF and Cassini missions. The CRAF/Cassini missions will be the first to use the next generation spacecraft using the Mariner Mark II design. The CRAF spacecraft (Comet Rendezvous Asteroid Flyby) will meet with the Comet Kopff near the orbit of Jupiter and travel along side it for at least three years. It will also launch a penetrator which will directly sample the comet's nucleus. On the way to to Comet Kopff, CRAF will flyby the asteroid Hamburga. JPL is currently in negotiations with the McDonald's hamburger franchise to arrange some kind of advertising deal (this is no joke). Key Scheduled Dates for the CRAF Mission -------------------------------------------- 08/22/95 - Titan IV/Centaur Launch 01/22/98 - 449 Hamburga Asteroid Flyby 08/14/00 - Comet Kopff Arrival 08/20/01 - CRAF Penetrator to Kopff 03/31/03 - End of Primary Mission The Cassini mission will go to Saturn, using gravity assists from the Earth and Jupiter. This trajectory is called EJGA (Earth-Jupiter Gravity Assist). A probe named Huygens will be dropped off at Saturn's largest moon, Titan. The Cassini mission is an international mission. The European Space Agency (ESA) will supply the Huygens probe, Germany will supply the propulsion module, and Italy will provide the High Gain Antenna, sun sensors, and radio science instruments. ESA has already approved the science instruments that will be on the Titan probe. NASA has selected the science instruments that will be onboard the Cassini orbiter; however, this list is not quite official yet -- it is sitting on the desk of Richard Truly, NASA's administrator, awaiting his signature. Key Scheduled Dates for the Cassini Mission (EJGA Trajectory) ------------------------------------------------------------- 08/22/96 - Titan IV/Centaur Launch 03/29/97 - 66 Maja Asteroid Flyby 06/08/98 - Earth Gravity Assist 02/06/00 - Jupiter Gravity Assist 12/06/02 - Saturn Arrival 03/27/03 - Titan Probe Release 03/29/03 - Orbiter Deflection Maneuver 04/18/03 - Titan Probe Entry 06/30/03 - Iapetus Flyby 05/20/04 - Dione Flyby 09/12/04 - Enceladus Flyby 08/14/05 - Iapetus Flyby 12/31/06 - End of Primary Mission The Maja asteroid that Cassini will encounter is a type C asteroid, 39 kilometers in size. When Cassini arrives at Saturn in December, 2002, it will perform a SOI (Saturn Orbit Insertion) burn. The spacecraft will actually pass through the outer rings of Saturn during SOI, passing between the F and G rings at a distance of 2.6 Saturn radii from the planet. After SOI, the Huygens probe will be released on the subsequent orbit. Two days after probe release, the Cassini orbiter will perform a deflection manuever. This deflection maneuver serves two purposes: it ensures the Cassini orbiter doesn't follow the Hugyens probe into Titan, and it positions the orbiter to lag behind the probe about 3.5 hours so that science data can be received from the Huygens probe as it descends into the atmosphere of Titan. It will take the Huygens probe about 3 hours to parachute all the way down to the surface of Titan; if the probe survives the landing, valuable data will continue to be transmitted back for about 30 more minutes. No more data will be returned to the Cassini orbiter from Huygens on any subsequent orbits, as the battery onboard Huygens will have rundown by then. During its four year orbital tour of Saturn, Cassini will make 60 orbits of the planet. Compare this with Galileo, which will make about 10 orbits around Jupiter in two years. Galileo has the luxury of using gravity assists of the four large Galileon moons (Io, Europa, Ganymede and Callisto), while at Saturn, there is only one large moon, Titan, that Cassini can take advantage of. Because of this, Cassini will make close flybys of Titan on 35 of the 60 orbits. Each Titan flyby is designed so that the Cassini will be deflected a little further out of Saturn's ecliptic plane, so that at the end of four years, the spacecraft will be in polar orbit around Saturn at an inclination of between 80 to 90 degrees. A polar orbit puts Cassini into a unique advantage point where many star occultations can be observed through Saturn's rings. Cassini will be carrying a Titan Radar Mapper which it will use to map the surface of Titan during its numerous flybys of the moon. The Titan Radar Mapper is a SAR (Synthetic Aperture Radar), similiar to the one used by the Magellan spacecraft at Venus. Also, still being looked at, are alternate trajectory routes to Saturn. A VEJGA (Venus-Earth-Jupiter Gravity Assist) trajectory has been developed which would use an additional gravity assist of Venus. This trajectory has the advantage of reducing the launch energy, which in turn, means a heavier payload can be launched. Note that the VEJGA trajectory is only preliminary, and the EJGA trajectory is still the official route that Cassini will take. Key Dates for the Cassini Mission (VEJGA Trajectory) ---------------------------------------------------- 11/28/95 - Titan IV/Centaur Launch 12/04/96 - Venus Gravity Assist 07/05/98 - Earth Gravity Assist 11/11/98 - Clarissa Asteriod Flyby 03/28/00 - Jupiter Gravity Assist 12/07/03 - Saturn Arrival This trajectory will have Cassini pass near the Clarissa Asteroid, a type F asteroid which is 21 kilometers in size. ___ _____ ___ /_ /| /____/ \ /_ /| | | | | __ \ /| | | | Ron Baalke | baalke@mars.jpl.nasa.gov ___| | | | |__) |/ | | |___ Jet Propulsion Lab | baalke@jems.jpl.nasa.gov /___| | | | ___/ | |/__ /| M/S 301-355 | |_____|/ |_|/ |_____|/ Pasadena, CA 91109 |
sysmgr@KING.ENG.UMD.EDU (Doug Mohney) (11/12/90)
In article <1990Nov11.001924.10302@jato.jpl.nasa.gov>, baalke@mars.jpl.nasa.gov (Ron Baalke) writes: > >nucleus. On the way to to Comet Kopff, CRAF will flyby the asteroid >Hamburga. JPL is currently in negotiations with the McDonald's hamburger >franchise to arrange some kind of advertising deal (this is no joke). Does this mean that Ron Baalke will be replaced by Ronald McDonald for our news postings ? :-) > Also, still being looked at, are alternate trajectory routes to Saturn. >A VEJGA (Venus-Earth-Jupiter Gravity Assist) trajectory has been developed >which would use an additional gravity assist of Venus. This trajectory has >the advantage of reducing the launch energy, which in turn, means a heavier >payload can be launched. Could a Venus assist get the probe there faster instead of trading off for a heavier playload?
rice@dg-rtp.dg.com (Brian Rice) (11/13/90)
In article <0093F8EE.D9E16A40@KING.ENG.UMD.EDU>, sysmgr@KING.ENG.UMD.EDU (Doug Mohney) writes: |> In article <1990Nov11.001924.10302@jato.jpl.nasa.gov>, |> baalke@mars.jpl.nasa.gov (Ron Baalke) writes: |> > |> > On the way to to Comet Kopff, CRAF will flyby the asteroid |> > Hamburga. JPL is currently in negotiations with the McDonald's |> > hamburger franchise to arrange some kind of advertising deal |> > (this is no joke). |> |> Does this mean that Ron Baalke will be replaced by Ronald McDonald |> for our news postings ? :-) JPL: "Junkfood Promotion Lab." Seriously, I think Ron just threw this in to see whether or not people were really reading his articles. Either that or NASA really wants to have CRAF do a gravity-assist flyby someplace, and they're counting on the added mass of the Happy Meal to justify it. -- Brian Rice rice@dg-rtp.dg.com +1 919 248-6328 DG/UX Product Assurance Engineering Data General Corp., Research Triangle Park, N.C.
hthomas@irisa.fr (Henry Thomas) (11/13/90)
In article <7034.273fd310@abo.fi>, mlindroos@abo.fi writes: |> In article <1990Nov11.001924.10302@jato.jpl.nasa.gov>, baalke@mars.jpl.nasa.gov (Ron Baalke) writes: |> > |> > CRAF/Cassini Status Report |> > November 9, 1990 |> > ...take the Huygens probe about 3 hours to parachute all the way down to the |> > surface of Titan; if the probe survives the landing, valuable data will |> > continue to be transmitted back for about 30 more minutes. No more data will |> > be returned to the Cassini orbiter from Huygens on any subsequent orbits, as |> > the battery onboard Huygens will have rundown by then. |> > |> |> 30 minutes! Why can't we send an advanced long-life, Viking-style probe |> to Titan instead?! The Viking lander was "only" about twice as heavy as the |> Huygens probe will be so the lack of a powerful-enough launcher surely cannot |> be the reason? Is this just because of financial considerations again, or...? The reason is maybe that we have NO data of the condition down there: - Is there any *solid* ground ? - pressure ? - temperature ? So with no information, it seems difficult to design a long-life probe. A similar(?) problem occured on Venus, where the probes Venera 11-14 lasted only a few hours. The first ones didn't reached the ground because theirs parachutes where destroyed by the acid atmosphere. On mars, the informations where much more complete, because the ground had been observed by many orbital probes: it was visible. There was an excellent article in the ESA journal (?), some month ago about "Cassini Probe Huygens Entry techniques" . -- -- E-mail: Henry.Thomas@irisa.fr Henry Thomas - IRISA Campus Universitaire de Beaulieu 35042 RENNES CEDEX FRANCE Phone: (+33)99 36 20 00 +549 Fax: (+33)99 38 38 32 Telex: UNIRISA 950 473F X.400: C=FR;ADMD=ATLAS;PRMD=irisa;S=hthomas Telex:/X121=842950473/@atlas.fr
mlindroos@abo.fi (11/13/90)
In article <1990Nov11.001924.10302@jato.jpl.nasa.gov>, baalke@mars.jpl.nasa.gov (Ron Baalke) writes: > > CRAF/Cassini Status Report > November 9, 1990 > ...take the Huygens probe about 3 hours to parachute all the way down to the > surface of Titan; if the probe survives the landing, valuable data will > continue to be transmitted back for about 30 more minutes. No more data will > be returned to the Cassini orbiter from Huygens on any subsequent orbits, as > the battery onboard Huygens will have rundown by then. > 30 minutes! Why can't we send an advanced long-life, Viking-style probe to Titan instead?! The Viking lander was "only" about twice as heavy as the Huygens probe will be so the lack of a powerful-enough launcher surely cannot be the reason? Is this just because of financial considerations again, or...? MARCU$
joshi@public.BTR.COM (Nikhil R. Joshi joshi@btr.com) (11/14/90)
In article <1990Nov13.104319.11134@irisa.fr> Henry.Thomas@irisa.fr writes: >>In article <7034.273fd310@abo.fi>, mlindroos@abo.fi writes: >> >> 30 minutes! Why can't we send an advanced long-life, Viking-style probe >> to Titan instead?! The Viking lander was "only" about twice as heavy as the >> Huygens probe will be so the lack of a powerful-enough launcher surely cannot >> be the reason? Is this just because of financial considerations again, or...? > >The reason is maybe that we have NO data of the condition down there: > > - Is there any *solid* ground ? > - pressure ? > - temperature ? > Was the Viking lander at least partially solar powered? If so, that explains it's long life. The solar flux at Saturn isn't nearly great enough to power even an orbital probe like Voyager, let alone a lander after being attenuated by Titan's atmosphere. But then why can't we put an RTG like Voyager's on the probe? Nikhil Joshi joshi@btr.com
hthomas@irisa.fr (Henry Thomas) (11/14/90)
In article <1990Nov13.104319.11134@irisa.fr>, hthomas@irisa.fr (Henry Thomas) writes: |> In article <7034.273fd310@abo.fi>, mlindroos@abo.fi writes: |> |> In article <1990Nov11.001924.10302@jato.jpl.nasa.gov>, baalke@mars.jpl.nasa.gov (Ron Baalke) writes: [deleted] |> |> 30 minutes! Why can't we send an advanced long-life, Viking-style probe |> |> to Titan instead?! The Viking lander was "only" about twice as heavy as the |> |> Huygens probe will be so the lack of a powerful-enough launcher surely cannot |> |> be the reason? Is this just because of financial considerations again, or...? |> |> The reason is maybe that we have NO data of the condition down there: |> - Is there any *solid* ground ? |> - pressure ? |> - temperature ? |> So with no information, it seems difficult to design a long-life probe. |> A similar(?) problem occured on Venus, where the probes Venera 11-14 lasted only a few hours. The first ones didn't reached the ground because theirs parachutes where destroyed by the acid atmosphere. |> On mars, the informations where much more complete, because the ground had been observed by many orbital probes: it was visible. |> |> There was an excellent article in the ESA journal (?), some month ago about "Cassini Probe Huygens Entry techniques" . |> Here are some excerpts from this article ESA Journal 1989, vol 13 pp 175--190 "Cassini/Huygens Entry and Descent Technologies" G Scoon, G, Whitcomb, M Eiden, A. Smith "The main objectives of the probe's mission will be the determination of the chemical composition of the atmosphere and the measurement of winds and temperature and pressure profiles from an altitude of 170 km down to the surface" ... " Althoug