Phobos 1

1. Historical Background and Detailed Objectives

The Phobos 1 mission represented the Soviet return to Martian exploration following previous attempts by the Mars and Zond series, proposing a complex technological architecture that combined planetary orbital observation, cruise solar physics, and a close encounter with the moon Phobos. The scientific vacuum it aimed to fill ranged from the compositional characterization of the satellite to the dynamics of the interaction between the solar wind and the upper Martian atmosphere.

Engineering:

• Validate the new heavy interplanetary platform developed by NPO Lavochkin.
• Demonstrate three-axis stabilization using combined star and sun sensors with cold gas microthrusters.
• Execute complex orbital insertion and millimetric approach maneuvers to Phobos.
• Deploy a fixed automatic lander module (DAS) onto the surface of the moon Phobos.

Scientific:

• Study the morphology, internal structure, surface composition, and magnetic field of Phobos through low-altitude approaches.
• Characterize the Martian atmosphere, its thermal dynamics, and the ionosphere.
• Analyze the interaction of the solar wind with Mars' induced magnetosphere using plasma instrumentation (ASPERA).
• Observe solar oscillations, X-ray emissions, and the solar corona during the interplanetary cruise phase.
• Detect and locate gamma-ray bursts (GRBs) in the space environment.

2. Vehicle Architecture and Main Subsystems

The Phobos 1 probe featured a total launch mass of 6,220 kg with the ADU orbital insertion propulsion module attached, registering a dry mass without propellant of approximately 2,600 kg and an instrument payload of 540 kg. Its structure featured a height of 3.8 m and a wingspan of 8.2 m with the solar panels deployed. Power supply depended on two steerable solar panels capable of generating about 700 W of power at 1 AU, backed by nickel-cadmium accumulators. Communications were carried out using UHF, C, and X bands, employing a 1.6 m diameter high-gain parabolic antenna (HGA). Attitude control was entrusted to a three-axis stabilization system operated by sun and star sensors.

3. Payload and Scientific Instrumentation

The scientific payload integrated cutting-edge instruments provided by a broad international collaboration:

• VSK: Video spectrometry system for optical navigation and multispectral surface mapping.
• LIMA-D: Laser and mass spectrometer for remote ablation and chemical analysis of Phobos.
• DION: Krypton ion gun and secondary mass spectrometer for regolith study.
• TEREK: X-ray and optical telescope and coronagraph for solar physics (Phobos 1 exclusive instrument, developed jointly with Czechoslovakia).
• IPHIR: High-precision solar photometer for heliosismology and study of global oscillations.
• VGS and LILAS: Spectrometers for detecting solar flares and cosmic gamma-ray bursts.
• ASPERA: Ion analyzer and electron spectrometer for solar wind and plasma.
• SOVIKOMS: Particle and solar wind spectrometer.
• MAGMA / FGMM: Fluxgate magnetometers for measuring magnetic fields.
• APV-F: Plasma wave and oscillation analyzer with Langmuir probe.
• SUFR and RF-15: Extreme ultraviolet and solar X-ray photometers.
• DAS (Lander): Phobos surface probe equipped with accelerometer, TV camera, and Alpha-X and thermionic spectrometers.

4. Chronology and Mission Phases

Following its launch on July 7, 1988 from the Baikonur cosmodrome via a Proton-K rocket with a Blok D-2 stage, the probe was successfully injected into a transfer trajectory to Mars. During the interplanetary cruise phase, which extended until late August 1988, the solar and plasma instruments were successfully activated, recording heliosismic data and gamma-ray bursts. However, between August 29 and 30, 1988, the transmission of an erroneous telecommand from the ground station omitted a safety verification code, which allowed a test routine to be uploaded that deactivated the cold gas pneumatic thrusters. On September 2, 1988, the definitive failure of the scheduled telemetry session was verified, marking the total loss of signal from the probe.

5. Results and Discoveries

Despite its premature end, the operational cruise phase allowed valuable scientific data to be obtained. The IPHIR photometer successfully recorded global solar oscillations, providing significant heliosismic milestones. Likewise, the LILAS and VGS detectors detected multiple cosmic gamma-ray bursts and solar flares, while the magnetometers completed their calibration in the heliospheric medium.

6. Failure Analysis and Legacy

The loss of Phobos 1 was due to human error on the ground during the command transmission process, which deprived the vehicle of its orientation toward the Sun. Remaining without a solar lock, the panels stopped generating current, the batteries completely depleted in a few hours, and the probe remained chemically inert drifting in heliocentric orbit. The accumulated experience and the architecture of the international collaboration served as a technical basis for its twin mission, Phobos 2.