Mars Pathfinder

 1996-068A

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Mars Pathfinder was originally part of the cancelled NASA-Ames MESUR project. It became a NASA Discovery program mission developed at JPL.

At launch the spacecraft is 2.7m wide and 1.5m high. Mass is 880 kg (795 kg dry).

The craft has eight 4 N monopropellant hydrazine thrusters from cruise propulsion. At entry. mass is 585 kg including 324 kg lander.

The EDL (entry descent and landing) system has three Thiokol Star 5D RAD motors each 7.9 kN thrust. These burn for 2.2s (before the bridle is cut).

Star 5D is 0.83l 0.12dia with 17.6 kNs impulse, 5.6kN thrust for 3.0s and 256s Isp-eff, mass 10 kg full 3 kg dry.

Entry was at 14.06 deg at 3522 km radius (125 km above the 3397 km nominal radius) over 21.831 W, 22.630N with inertial velocity 7.264 km/s and azimuth 253.1 deg. Because the entry was retrograde, the relative velocity was 7.479 km/s. This corresponds to an orbit of -11 x -9793 km x 152 deg.

Entry speed 27000 kph; MPF slows with a heat shield and then deploys a 12.7m diameter parachute. The lander then separates from the backshell, remaining attached to it by a 20m bridle (tether). The 5-m diameter cluster of airbags then inflate. The three RAD motors fire for 2.25 seconds with 7.94kN each; after 2.0 seconds the bridle is cut and the airbag-enclosed lander falls to the surface, while the rockets pull the parachute away from the landing site. MPF bounced across the surface for several minutes and about one kilometer. Then the air bags slowly deflate over three hours. The lander deploys petals to turn itself upright and deploys the six-wheeled Sojourner micro-rover.

After launch on 1996 Dec 2, MPF experienced problems with a sun sensor, but flight controllers successfully programmed a workaround. The spacecraft was inserted into a Type I fast transfer orbit to Mars. B-plane miss distance at launch was 477000 km with a closest approach at 0915 UTC on 1997 Jul 3, reduced to a 4800 km miss by TCM-1 and 2.

Landing on 1997 Jul 4 was at 19.33N, 33.55W. On Jul 6, the lander was renamed the Carl Sagan Memorial Station after the planetary scientist and science popularizer (1934-1996).

Landed mass included airbags is 370 kg.

MPF
Date	Time	Event	Orbit
1996 Dec 4	0658:07	Launch	CC LC17B
	0659:10	SRM x 6 burnout
	0659:12	SRM x 3 burn
	0659:13	SRM x 6 sep
	0700:16	SRM x 3 burnout
	0700:18	SRM x 3 sep
	0702:28	MECO
	0702:34	VECO
	0702:36	Stage 1 sep
	0702:41	Stage 2 burn
	0702:46	Fairing sep
	0707:35	SECO 1	173 x 191 x 28.7
	0804:29	Stage 2 restart over KMR
	0806:01	SECO 2	177 x 3083 x 28.7
	0806:51	Spinup
	0806:54	Stage 2 sep
	0807:32	Stage 3 burn
	0808:59	Stage 3 burnout
	0813:37	Yoyo despin
	0813:42	Stage 3 sep
		Stage 2 depletion	148 x 3119 x 36.4
1996 Dec 4	1200:00	Range 76352 km
	1710	Pass EL1:4
1996 Dec 9	0940?	Pass L1 sphere
		Solar orbit	0.986 x 1.597 AU x 0.10 deg
1997 Jan 1	1200	Range to Earth 7.707Mkm
1997 Jan 10	0200	TCM-1, 90 min burn 31.2 m/s
1997 Feb 3	2300	TCM-2 1.6m/s
1997 May 7	0100	TCM-3 0.1m/s
1997 Jun 25	1700	TCM-4A 1.6s 0.02m/s
	1745	TCM-4B 2.2s
1997 Jul 1	1200	Range 1.485Mkm
1997 Jul 2	0700	MPF range 1.1 Mkm to Mars
	0845	Enter Mars sphere 1.082Mkm
1997 Jul 2	1200	Range 1.023Mkm
1997 Jul 3	1200	Range 561674 km
1997 Jul 4	0700	MPF range 195000 km to Mars
	1200	MPF range 98391 km to Mars
1997 Jul 4	1622	Cruise stage sep, E -30 min
1997 Jul 4	1651:50	E, Entry at 125 km, mass 570 kg
	1652:54s	E+1:04 Peak heating, 40 km
1997 Jul 4	1654:42	E+2:52, para deploy at 10 km, 1600 kph
1997 Jul 4	1655:02	E+3:12, heatshield sep
1997 Jul 4	1655:18	E+3:28, tether deploy
1997 Jul 4	1655:21	E+3:31, tether deployed
1997 Jul 4	1656:45	E+4:55, airbag deploy. 300m
1997 Jul 4	1656:49	E+4:59, RAD firing, 98m 225 kph
1997 Jul 4	1656:51	E+5:01 Tether and backshell sep, 21m
1997 Jul 4	1656:53	E+5:03 RAD burn ends 2.25s
1997 Jul 4	1656:55	E+5:05 Landing on Mars, 10 m/s