Phobos F

The Phobos project involved two large Mars orbiters, Phobos 1 and Phobos 2 (Sagdeev et al., 1988; TsUP, 1988). Their main target was Phobos itself, the larger of Mars' two moons, being 26.1 X 22.2 X 18.6 km in size and probably a captured asteroid. Amongst the payloads were two types of lander, a stationary lander (on both) and a hopping rover (on Phobos 2 only). Sadly, Phobos 1 was lost during cruise and Phobos 2 was lost in Martian orbit, before the low altitude 50 m) hovering phase during which the landers were to be deployed to the surface. However, at the time of writing, Russia has a Phobos sample return project under way, named Phobos-Grunt (Marov et al., 2004).

20.1.1 Phobos 1,2 DAS

Phobos 1 and 2 each carried a 'long-lived autonomous station' (Russian abbreviation: DAS) to enable the study of Phobos' orbit (which is thought to be slowly spiralling in towards Mars) and libration by means of radio science and Sun-sensor data. Other in situ instruments were also included (Figure 20.1).

Target Objectives Prime contractor Launch site, vehicle

Launch date

Arrival date Landing site co-ordinates End(s) of mission(s) Mass(es) Payload experiments

Delivery architecture Thermal aspects Power aspects Communications architecture EDL architecture

Landing speed(s) Active operations

(deployments, etc.) Key references

Phobos

Measurement of the orbit of Phobos and its libration

NPO Lavochkin (formerly OKB-301)

Baikonour, Proton 8K82K / 11S824F (on Phobos 1 & 2)

Phobos 1 Phobos 2

07/07/1988 12/07/1988

Deployment was due March/April 1989

DAS lifetime on surface designed to be >3 months

67 kg, 20.6 kg payload

• TV camera (Blamont, Kerzhanovich)

• ALPHA-X alpha-proton-X-ray spectrometer

(Hovestadt; Mukhin)

(Blamont, Linkin)

• Seismometer (Khavroshkin, Tsyplakov, Linkin)

• RAZREZ anchor penetrometer (Khavroshkin, Tsyplakov)

• Celestial mechanics experiment (Linkin, Preston, Blamont) The Project Scientist was Viacheslav M. Linkin

Separation from Phobos orbiter at 2.2 m s"1 during low altitude flyover Details unknown (thermal blanket on electronics boxes) Solar arrays, secondary battery

Two-way DTE at 1672 MHz; transmission rate 4-20 bits s"1

Spin-stabilisation at 62 rad s"1 during descent; detection of surface with contact probes; firing of hold-down thrusters and anchoring harpoon (100 m s"1); deployment of upper section followed by deployment and pointing of solar arrays and antenna 0-4 m s"1 vertical, 2 m s"1 horizontal Descent and landing aspects; deployment of ALPHA-X

sensor heads; solar array pointing mechanism Sagdeev et al., 1988; TsUP, 1988

Figure 20.1 Phobos DAS.

20.1.2 Phobos 2 PROP-F

PROP-F was a mobile surface element due to be deployed from the Phobos 2 orbiter. It was due to land and perform a sequence of physical and compositional properties measurements at multiple locations. Motion was actuated by a single 'foot' in its circular base, and it used a system of four control rods (one static pair and one rotating pair) to bring itself upright at each new site, ready to perform the next measurement sequence. Sadly Phobos 2 was lost before PROP-F could be deployed (Figure 20.2).

Target Objectives

Prime contractor

Launch site, vehicle Launch date Arrival date Landing site co-ordinates End(s) of mission(s)

Mass(es) Payload experiments

Delivery architecture

Phobos

In situ measurements of physical and compositional properties of Phobos' surface material at several locations VNIITransMash

Baikonour, Proton 8K82K/11S824F (on Phobos 2) 12/07/1988

PROP-F was due to be deployed in March/april 1989

PROP-F not yet deployed when Phobos 2 lost on 27/03/1989. The envisaged total time of operation was 4 h, during which — 7 measurement cycles were expected. 50 kg

• ARS-FP automatic X-ray fluorescence spectrometer

(Surkov)

• Ferroprobe magnetometer (Dolginov)

• Kappameter magnetic permeability/susceptibility sensor

(Dolginov)

• Gravimeter (Ksanfomaliti)

• T sensors (Ksanfomaliti)

• BISIN conductometer/tiltmeter (Gromov)

• Mechanical sensors (Kemurdzhian):

• Penetrometer

• UIU accelerometer

• Sensors on hopping mechanism Total 7 kg.

The Project Scientist was Aleksandr L. Kemurdzhian Separation from Phobos orbiter during low altitude flyover, with velocity relative to orbiter of 3 m s-1 horizontal component and 0.45 m s Free fall to surface.

downward vertical component.

Thermal aspects

Unknown

Power aspects

Battery

Communications

One-way (?) relay via Phobos 2 orbiter

architecture

EDL architecture

Free fall to surface. Time to come to rest after

initial impact and subsequent bouncing — 45 min.

Ejection of damper and righting of lander using

control rods

Landing speed(s)

Initial impact: <1 m s-1 vertical, —3 m s horizontal

Active operations

Hopping manoeuvre, movement of rotating arms to

(deployments, etc.)

bring itself upright, penetrometer operational

sequence

Key references

Kemurdzhian et al., 1988,1989a,b, 1993

Figure 20.2 Phobos 2 PROP-F.
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