The Heat Flow and Physical Properties Package HP3 for the InSight mission will attempt the first measurement of the planetary heat flow of Mars. The data will be taken at the InSight landing site in Elysium planitia (136 ∘E, 5 ∘N) and the uncertainty of the measurement aimed for shall be better than ±5 mW m−2. The package consists of a mechanical hammering device called the “Mole” for penetrating into the regolith, an instrumented tether which the Mole pulls into the ground, a fixed radiometer to determine the surface brightness temperature and an electronic box. The Mole and the tether are housed in a support structure before being deployed. The tether is equipped with 14 platinum resistance temperature sensors to measure temperature differences with a 1-σ$\sigma $ uncertainty of 6.5 mK. Depth is determined by a tether length measurement device that monitors the amount of tether extracted from the support structure and a tiltmeter that measures the angle of the Mole axis to the local gravity vector. The Mole includes temperature sensors and heaters to measure the regolith thermal conductivity to better than 3.5% (1-σ$\sigma $) using the Mole as a modified line heat source. The Mole is planned to advance at least 3 m—sufficiently deep to reduce errors from daily surface temperature forcings—and up to 5 m into the martian regolith. After landing, HP3 will be deployed onto the martian surface by a robotic arm after choosing an instrument placement site that minimizes disturbances from shadows caused by the lander and the seismometer. The Mole will then execute hammering cycles, advancing 50 cm into the subsurface at a time, followed by a cooldown period of at least 48 h to allow heat built up during hammering to dissipate. After an equilibrated thermal state has been reached, a thermal conductivity measurement is executed for 24 h. This cycle is repeated until the final depth of 5 m is reached or further progress becomes impossible. The subsequent monitoring phase consists of hourly temperature measurements and lasts until the end of the mission. Model calculations show that the duration of temperature measurement required to sufficiently reduce the error introduced by annual surface temperature forcings is 0.6 martian years for a final depth of 3 m and 0.1 martian years for the target depth of 5 m.

中文翻译：

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InSight 任务的热流和物理特性包 (HP3)

InSight 任务的热流和物理特性包 HP3 将尝试首次测量火星的行星热流。数据将在 Elysium 平原 (136 ∘E, 5 ∘N) 的 InSight 着陆点采集，目标测量的不确定度应优于 ±5 mW m-2。该包裹包括一个称为“鼹鼠”的机械锤击装置，用于穿透风化层，鼹鼠拉入地下的仪器系绳，一个用于确定表面亮度温度的固定辐射计和一个电子盒。在部署之前，鼹鼠和系绳被安置在一个支撑结构中。系绳配备 14 个铂电阻温度传感器，以 1-σ$\sigma $ 不确定度为 6.5 mK 来测量温差。深度由系绳长度测量装置确定，该装置监测从支撑结构中提取的系绳量，以及测量鼹鼠轴与局部重力矢量的角度的倾斜计。鼹鼠包括温度传感器和加热器，使用鼹鼠作为改进的线热源，测量风化层的热导率优于 3.5% (1-σ$\sigma$)。鼹鼠计划前进至少 3 m——足够深以减少日常地表温度强迫的误差——并深入火星风化层 5 m。着陆后，HP3 将在选择仪器放置地点后由机械臂部署到火星表面，以最大限度地减少着陆器和地震仪造成的阴影干扰。然后鼹鼠将执行锤击循环，一次向地下推进 50 厘米，然后是至少 48 小时的冷却期，以便让锤击过程中积聚的热量消散。达到平衡热状态后，进行 24 小时的热导率测量。重复此循环，直到达到 5 m 的最终深度或无法进一步前进。随后的监测阶段包括每小时的温度测量，并持续到任务结束。模型计算表明，为了充分减少年表面温度强迫引入的误差，温度测量持续时间对于 3 m 的最终深度为 0.6 火星年，对于 5 m 的目标深度为 0.1 火星年。进行 24 小时的热导率测量。重复此循环，直到达到 5 m 的最终深度或无法进一步前进。随后的监测阶段包括每小时的温度测量，并持续到任务结束。模型计算表明，为了充分降低年表面温度强迫引入的误差，所需的温度测量持续时间对于 3 m 的最终深度为 0.6 火星年，对于 5 m 的目标深度为 0.1 火星年。进行 24 小时的热导率测量。重复此循环，直到达到 5 m 的最终深度或无法进一步前进。随后的监测阶段包括每小时的温度测量，并持续到任务结束。模型计算表明，为了充分减少年表面温度强迫引入的误差，温度测量持续时间对于 3 m 的最终深度为 0.6 火星年，对于 5 m 的目标深度为 0.1 火星年。