PolyU is to design and produce a Mars Landing Surveillance Camera (Mars Camera), which will be located on the outside top surface of the Mars Lander. The Mars Camera will monitor the deployment status of the Mars Rover with respect to the status of the solar panel, antenna, as well as the rover's movement. The information is critical for the successful movement of the Mars Rover onto the Mars surface.
To capture ultra-wide angle images on Mars for scientific research, the
Mars Camera has to have a wide field of vision with low distortion
optics within the little allowable payload, but at the same time be able
to withstand extreme temperature variation, mechanical impact and
vibration within the little available mass. What’s more, high
reliability is required under the extreme space travel environment
digital manufacturing in poly u
It is collaboration between The Hong Kong Polytechnic University (PolyU) and the China Academy of Space Technology (CAST)
The lander — which, at 530 pounds, is nearly twice the mass of the rovers China sent to the moon — has six instruments that it will employ over 90 days on the surface. They include ground-penetrating radar to study the planet’s geology and search for potential underground reservoirs of ice — a key to sustaining an extended human presence in space. The main candidate for a landing site, the scientists said, is Utopia Planitia, a 2,000-mile wide basin where NASA’s Viking 2 landed in 1976.
- Retropropulsion will be responsible for slowing the spacecraft during its final descent. Most of this will be provided by a 7,500-Newton variable thrust engine, like the main engine used by China’s Chang’e-3 and -4 lunar landers. The lander will employ a laser range finder and a microwave ranging velocity sensor to gain navigation data—technology that was also developed initially for China’s moon missions.
- The lander will separate from the main body of the spacecraft at an altitude of 70 meters, according to Zhang Rongqiao, mission chief designer, and enter a hover phase to search for a safe landing spot. 3D laser scanning, or lidar, will provide terrain data such as elevation. Obstacle-avoiding mode, facilitated by optical cameras, will begin at 20 meters above the surface.
- Some of these processes are apparent in this mesmeric footage of the Chang’e-4 landing. An obstacle avoidance phase is apparent as the spacecraft makes its descent to the crater-covered lunar surface which appears fractal in nature.
TBD:
camera sensor resolution
pixel size
focal length
this camera system is based on CIVA (Comet Infrared and Visible Analyser) from Switzerland.
The main difference is the fov, increased from 60 degrees to
a wide-angle field of view (a maximum of 120 degrees horizontally and a maximum of 170 degrees diagonal)
理大校长滕锦光教授说：“理大很荣幸有两支跨学科科研团队参与其中，分别为火星着陆区的地形测量和评估，以及落火状态监测相机（即火星相机）的研製作出贡献。理大也已於近日成立了由容启亮教授领导的深空探测研究中心，将继续不遗余力支持更多航天技术的研发，致力以科研力量贡献国家发展。
「大約在2017年底開始醞釀，做了一些準備功夫，翌年8月正式簽約，隨即全速去做（火星相機），」理大工業及系統工程學系鍾士元爵士精密工程教授、精密工程講座教授及副系主任容啟亮憶述團隊參與是次國家火星探測任務之始，雖然他們過往有做過精密的相機項目，但要達到「落火」規格，必先要實現多項變革，「要全面重新設計過，包括相機結構，電子零件如何擺法，線路、部件，應該用上什麼才可承受火星環境。」
眾多難題之中，容啟亮首先點出了重量這項關鍵，「這是其中一大重要限制，我們只能夠在很有限的重量下打造相機，必須跟足要求，分毫不差。」火星相機重約390克，即只有不足1磅重，他笑言當初收到這項指標時，確實感覺挑戰很大，但也只得法寶盡出，達到目標。
設計輕巧不容易 還須兼顧強度
設計輕巧本身已不容易，還需要兼顧強度，使其足以承受太空環境以至「落火」衝擊，難上加難。「『天問一號』有好幾部相機，安裝位置各異，承受的衝擊亦各有不同，」容啟亮介紹其火星相機除了需要承受一般航天過程會遇到的衝擊外，由於位置比較接近「火工鎖」，因此還須承受一些額外衝擊，「航天儀器的一些部件本身會用螺絲鎖實，想要將其釋放，就要透過爆破將其切斷，這個（火工鎖）衝擊力很大，因此設計相機時亦必須顧及這點，使其抵受旁邊的爆炸震盪後，仍可正常運作。」 相機須承受相等於6200倍地球地心吸力（約飛機黑盒可受力兩倍）的衝擊震盪 即飛機黑盒可受力兩倍的衝擊震盪
另外，火星相機亦須要抵禦整段太空旅程及火星的低溫環境，「低溫起動又是另一大難題，即使我們會設加熱器，以免相機過於低溫，但亦非時刻都能保持，」容啟亮解釋，所謂低溫大約是零下45度左右，而火星相機在測試階段則能夠達到「零下75度以下，放足一年仍能正常運作」的成績，所以是有「走盞」的。
「即使美國都不是每次成功」
克服各種技術難關，團隊最終在去年2月成功研製並交付「火星相機」，但由於疫情關係，容啟亮無法前往內地見證「落火」，只得在港等候消息。對於國家首次執行「落火」任務，他形容挑戰確實很高，「即使美國都不是每次成功，尤其他們一般會事先於火星設環繞器，將火星攝得清楚後，再行揀選着陸點，最後才直接飛一個着陸器過去，分開不同階段完成。」
There are two such surveillance cam on the Mars lander. One in front of the rover( camera A) and one at the back ( camera B)
留言
張貼留言