Vesta was a planned multiple-asteroid-flyby mission that the Soviet Union assessed in the 1980s.
The Vesta mission would have consisted of two identical probes (just like earlier Soviet Venus missions), to be launched in 1991. Similar to the
Vega program
The Vega program (Cyrillic: ВеГа) was a series of Venus missions that also took advantage of the appearance of comet 1P/Halley in 1986. ''Vega 1'' and '' Vega 2'' were uncrewed spacecraft launched in a cooperative effort among the Soviet ...
, each spacecraft would deploy one or more landers or balloons into the Venusian atmosphere, and then proceed to its next target.
At Venus, a French satellite dedicated to asteroid flybys would be released. It would return for an Earth
gravity assist
In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing-by is the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the p ...
, and then reach about 3–3.3
au from the Sun. There they would fly by some smaller asteroids, and Vesta, if possible, with a small probe landing there.
The exact targets would depend on the launch date. In the initial 1985 study, 2700 possible trajectories were analyzed for a launch date in 1991/1992. Considering all constraints, about 12 candidate trajectories were selected. The two identical spacecraft could have different trajectories and targets. These included
5 Astraea
Astraea () (minor planet designation: 5 Astraea) is an asteroid in the asteroid belt. Its surface is highly reflective and its composition is probably a mixture of nickel–iron with silicate mineral, silicates of magnesium and iron. It is an S- ...
,
53 Kalypso,
187 Lamberta,
453 Tea,
1335 Demoulina and
1858 Lobachevskij, and
comet Encke
Comet Encke , or Encke's Comet (official designation: 2P/Encke), is a periodic comet that completes an orbit of the Sun once every 3.3 years. (This is the shortest period of a reasonably bright comet; the faint main-belt comet 311P/PanSTARRS ha ...
.
Spacecraft design
Around 1985 Vesta was changed to be a Mars mission, with the asteroid mission unchanged. Detailed plans called for each probe to visit four small bodies, including asteroids belonging to different classes - providing a representative sample of the diversity of asteroids - and probably one or two comets as well.
Visiting at least one
Apollo
Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label= Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label ...
-
Amor (Earth-nearing) asteroid was also given a preference.
Preliminary studies called for at least the following scientific instruments to be included:
* a wide angle camera (~6.5° field of view, 512×512 pixel
CCD)
* a narrow angle camera (~0.5° field of view, 512×512 pixel CCD - 3.9 arcsec/pixel)
* a
near-infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...
spectrometer
A spectrometer () is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where the ...
(measuring between 0.5–5
μm with λ/Δλ = 50, 5 arcminutes per pixel)
Possible further instrumentation:
*
UV spectrometer (for imaging during a comet flyby)
*
radar altimeter
A radar altimeter (RA), also called a radio altimeter (RALT), electronic altimeter, reflection altimeter, or low-range radio altimeter (LRRA), measures altitude above the terrain presently beneath an aircraft or spacecraft by timing how long it t ...
/
radiometer
* a dust detector
* ion or neutral gas detector
Onboard memory would be about 240
Mb. Images at closest approach (~500
km) could have a resolution of 10 m/pixel. Worst case downlink rate is 600 bit/second (if not using NASA's
Deep Space Network
The NASA Deep Space Network (DSN) is a worldwide network of American spacecraft communication ground segment facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that supports NASA's interplanetary ...
(DSN)). The scientific payload is about 100
kg. The spacecraft had 750 kg dry mass, and carried 750 kg propellants, and possibly a 500 kg penetrator. 20 square meters of solar panels provided 350
W of power.
If DSN support could have been obtained, Doppler tracking of the Vesta spacecraft's movement could accurately determine the mass of the encountered bodies. Should it not, another possibility was considered: releasing a test mass, and observing its movement near the target asteroid.
The spacecraft's structure was derived from telecommunication satellites (
INMARSAT), having the required mass, volume, and
delta-v
Delta-''v'' (more known as " change in velocity"), symbolized as ∆''v'' and pronounced ''delta-vee'', as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such a ...
capabilities (3-axis stabilized, with a pointing platform with 2 axes of freedom for scientific instruments).
Trajectory
The Mars
gravity assist
In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing-by is the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the p ...
constrains the possible trajectories. The asteroid penetrator also imposes limits on the speed of the approach of the target asteroid (less than 4 km/s).
Nevertheless, 3 possible trajectories were designed, with two Mars gravity assists.
A single Mars swing-by is also possible, but the double gravity assist increases the mass budget of the spacecraft by 30%, at the cost of an additional 1.8 year in travel time to the asteroid belt. The following trajectories are for the 1994 launch window. The size and type of each asteroid is also shown here:
Trajectory 1:
:launch from Earth
:Mars gravity assist
:flyby of
2335 James (a 10 km X-type asteroid) (an Amor-asteroid)
:Mars gravity assist
:
109 Felicitas (C-type, 76 km)
:
739 Mandeville (EMP(?) type, 110 km)
:
4 Vesta
Vesta ( minor-planet designation: 4 Vesta) is one of the largest objects in the asteroid belt, with a mean diameter of . It was discovered by the German astronomer Heinrich Wilhelm Matthias Olbers on 29 March 1807 and is named after Vesta, t ...
(V-type, or Vestoid. Has a diameter of 570 km) flyby with 3.5 km/s. A penetrator is released.
Total delta-v: 450 m/s
Trajectory 2:
:launch from Earth
:Mars gravity assist
:flyby of the
157P/Tritton short period comet
:Mars gravity assist
:
2087 Kochera(30 km?)
:
1 Ceres (flyby & releasing a penetrator)
Total delta-v: 1150 m/s
Trajectory 3:
:launch from Earth
:Mars gravity assist
:
1204 Renzia (10 km?) (an Amor-asteroid)
:Mars gravity assist
:
435 Ella (U type, 30 km)
:
46 Hestia
Hestia ( minor planet designation: 46 Hestia) is a large, dark main-belt asteroid. It is also the primary body of the Hestia clump, a group of asteroids with similar orbits.
Hestia was discovered by N. R. Pogson on August 16, 1857, at the Radc ...
(F type, 165 km)
:
135 Hertha
Hertha (minor planet designation: 135 Hertha) is an asteroid from the inner region of the asteroid belt, approximately in diameter. Discovered on 18 February 1874 by German–American astronomer Christian Peters at the Litchfield Observatory ne ...
(M type, 80 km)
Total delta-v: 350 m/s
In other studies
11 Parthenope
Parthenope ( minor planet designation: 11 Parthenope) is a large, bright main-belt asteroid.
Parthenope was discovered by Annibale de Gasparis on 11 May 1850, the second of his nine asteroid discoveries. It was named after ''Parthenopē'', on ...
,
19 Fortuna
Fortuna ( minor planet designation: 19 Fortuna) is one of the largest main-belt asteroids. It has a composition similar to 1 Ceres: a darkly colored surface that is heavily space-weathered with the composition of primitive organic compounds, i ...
and
20 Massalia were also considered.
Cancellation
A combination of factors, probably including changing Franco-Soviet relations, the partial failure of the Phobos mission, financial troubles and the disbanding of the Soviet Union, prevented the project from advancing beyond the planning phase.
References
{{Comet spacecraft
Cancelled spacecraft
Missions to asteroids
Soviet Venus missions
Missions to Mars
Soviet Mars missions
France–Soviet Union relations
Missions to comets