Description of the Mars 96 Mission

For more information, see the Mission Page at IKI in Russia

Mars '96 is a Russian mission to Mars scheduled to be launched in November/December 1996. The spacecraft (S/C) consists of an orbiter and four landers (two small, moderately soft landers and two penetrators). Only a single S/C will be launched during this opportunity. The mission consists of seven phases: launch and injection towards Mars, cruise (including 2 midcourse corrections), small station release and orbiter deflection maneuver, orbit insertion, orbit corrections, penetrator release, and mapping operations.

1. Launch and Trans-Mars Injection

    Mars '96 is scheduled to launch in late November 1996 from the Baikonur Cosmodrome. The first three stages and the first firing of the fourth stage of the Proton launch vehicle will be used to place the S/C into a 165 km, 51.6° inclined orbit. At the end of the first orbit, the fourth stage will be reignited to provide 3150 m/sec of the required 3725 m/sec necessary for Trans-Mars Injection (TMI). The remaining 575 m/sec needed to inject the 6 metric ton vehicle on its trajectory to Mars will be provided by the S/C propulsion module. Antenna deployments will occur between the 4th stage and S/C burns; solar array and PAIS platform deployments will occur after TMI.

Figure from IKI Mars '96 Mission Page

2. Cruise

    Mars '96 will follow a Type-2 interplanetary trajectory to Mars. After about 10 months in transit, arrival is scheduled for 12 September 1997. Two midcourse corrections are planned: the first after 7-10 days, the second about one month before arrival at Mars. Total anticipated Delta-V is less than 35 m/sec. A third correction will occur in conjunction with the orbiter deflection maneuver about 4-5 days prior to Mars Orbit Insertion (MOI).

3. Small Station Release and Orbiter Deflection Maneuver

    Approximately five days prior to MOI, the two small stations will be jettisoned, and the Orbiter will perform a deflection maneuver of about 35 m/s to place it on a trajectory to enter Mars orbit. The two stations will approach Mars independently. Their atmospheric entry velocity will be < 5.75 km/s, their entry angles between 10.5° and 20.5° , and their entry azimuth between 115° and 145° . Their landing site dispersion ellipses are ± 10° (600 km) along track and ± 2° (120 km) cross-track. All candidate landing sites are situated on the day-side of Mars, in Arcadia Planitia. The primary sites are 41.31° N, 153.77° W and 32.48° N, 169.32° W. A backup site has been identified at 3.65° N, 193° W.

Figure from IKI Mars '96 Mission Page

4. Mars Orbit Insertion

    At the periapsis of the approach hyperbola, the S/C propulsion system will be autonomously fired to place the the Orbiter into an initial orbit with a period of 43.09 ± 8.5 hr, and periapsis and apoapsis altitudes of 500 ± 200 and 52,000 km, respectively. Initial orbit inclination is 106.4° , and the latitude of periapsis is 26° North. The MOI Delta-V is 1020 m/sec.

5. Orbit Corrections

    Following MOI, the periapsis altitude will be adjusted to 300 km. Several additional orbit maneuvers, taking between 7 and 28 days, will be performed to phase the orbit for communications to Earth.

6. Penetrator Release

    Owing to the possible dispersions in the initial orbital period, the date for penetrator release may vary from 7 to 28 days. After the orbit is adjusted for communications with the Earth, the intent is to deploy one of the penetrators close to the small stations, and the other at a greater distance (at least 90° in longitude). If, however, the orbit phasing takes longer than expected, or dust storms begin, both penetrators can be deployed during the same telecommunications pass with the Earth. Under this condition, the separation of the penetrators will be less (5-6° ).

    For deployment, the Orbiter will first be properly oriented. The penetrator to be released will be spun about its longitudinal axis for stability and ejected. The penetrator's solid rocket motor will be ignited after moving a safe distance away from the Orbiter; the burn will place the penetrator into a atmospheric entry trajectory. Entry occurs 21-22 hours later. It is possible to deploy both penetrators on a single orbit. In the martian atmosphere, the probes undergo aerodynamic braking, first using a rigid cone and then an air-inflated braking device, until a given velocity is reached to provide their penetration into martian regolith. The entry velocity is 4.9 km/s at an entry angle of 12± 2°. The landing site error ellipse is ± 4° (240 km) along-track and ± 0.5° (30 km) cross-track. The penetrator impacts the surface at a velocity of 80 ± 20 m/s and the forebody separates from the aftbody. The penetrating part of the probe forebody, carrying the scientific and housekeeping instrumentation, enters the regolith down to 5-6 m, while the aftbody, with the rest of the instrumentation, remains on the surface. Scientific studies begin after penetration. Data are relayed to Earth by the Orbiter.

Figure from IKI Mars '96 Mission Page

7. Orbital Operations

    The orbital operations phase of the mission includes two sub-phases: support for the landed packages and orbital mapping. The orbital period will be adjusted to permit relay of the lander data. The orbital period permits 5-6 minute relays every seven days. Orbit corrections of about ± 0.07 m/sec (± 1.8 minutes orbital period or ± 110 km in groundtrack position) will be performed once a month to maintain the communications link with the landers.

    Once the penetrators have landed, the S/C propulsion module will be jettisoned and the ARGUS science platform deployed. After 50-60 days, the orbit periapsis will precess into the illuminated portion of Mars, and the Orbiter's surface and atmosphere instruments will be used extensively. The best illumination conditions will be encountered about 90 days in orbit. At this time, the orbital period will be adjusted to permit a 1° shift of ground tracks every 4 days. After this adjustment, the Orbiter will not be able to view the landers for data relay. Six additional orbit corrections are budgeted for orbit sustenance (Delta-V < 45 m/sec).

8. Other Relevant Mission Information

    The Mars 96 orbit periapsis migrates from 25° to 55° North latitude over a 24 month period. Periapsis migrates from a sun elevation angle of -25° to +38° for the first 8 months of the mission, and then decreases for the next 16 months.

    Tracking from the Evapatoria and Ussurijsk facilities varies from a maximum of around 8 hrs (angle > 7° ) to about 6.5 hr two months after MOI. Joint visibility decreases from 1.5 hr to 0.1 hr during this time.

    Solar conjunction occurs in May 1998:

    	Sun-Mars-Earth angle	 Dates
    		< 2		1-26 May
    		< 1		8-20 May
    		<0.1		13-14 May
    After the Orbiter completes its primary mission, aerobraking will be used to attempt to lower the orbital period from 43 to 8-10 hours.

to Mars 96 Index

to Mars 96 Science Objectives

to Mars 96 Mission Description

to Mars 96 Orbiter

to Mars 96 Orbiter Surface and Atmosphere Payload

to Mars 96 Orbiter Space Physics/Plasma Payload

to Mars 96 Orbiter Astrophysics/Cruise Payload

to Mars 96 Small Stations

to Mars 96 Small Station Payload

to Mars 96 Penetrators

to Mars 96 Penetrator Payload

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