CLICKS (13)

CMO CLICKS (13)

The Mars Surveyor 1998 Project

cited from CMO #202 (25 April 1998 issue)

The CMO is a bulletin of the OAA Mars Section published monthly (since 1986)

Science Phasing Orbit of the Mars Global Surveyor began from the beginning of April 1998 and the Mars Orbiter Camera (MOC) is now working (with the narrow and wide angle cameras). The Orbiter will continue for about six months during which some scientific acquisitions will be gained until the final phase of aerobraking begins (for four months). Mars will have by then moved around the Sun to a point where aerobraking can be resumed so that aerobraking will bring the orbit down into the 2 hour circular mapping condition at precisely the correct lighting condition. The mapping orbit conditions will be reached in January 1999 and mapping will actually begin in March 1999. During mapping, the spacecraft will take data all around the orbit because the high gain antenna will be deployed and able to track the Earth, and the solar panels can track the sun while the instruments are always pointed directly down at the Martian surface.

The Mars Surveyor 1998 project was announced this February from NASA's JPL and a detail can be obtained through the URL: http://www.jpl.nasa.gov
This 1998 Mars lander and orbiter missions are designed to learn more about the history of Mars' climate and the behaviour of related Martian volatiles, such as water vapour and ground ice. The orbiter named Mars Climate Orbiter (MCO), scheduled for launch on 10 Dec, will conduct a two-year primary mission to profile the Martian atmosphere and map its surface. The lander named Mars Polar Lander (MPL) will touch down in late 1999, scheduled for liftoff on 3 Jan 1999, will carry out a three-month mission to search for traces of subsurface water in this frozen, layered terrain and any evidence of a physical record of climate change. Note that the arrivals of both crafts will be late for our terrestrial observations in 1999: A datum summary is given as follows: where the season (by Ls) and the apparent diameter of Mars seen from the Earth are supplemented.

      Launch         Arrival 
MCO  10 Dec 1998   23 Sept 1999 (211°Ls, App.Diam=7.1")
MPL  03 Jan 1999   03 Dec  1999 (256°Ls, App.Diam=5.5")

The possible landing zone of MPL is interesting because it is to the south of the 70°S well in the south polar region and should be chosen "the best spot to land, one that presents a balance between lander safety and scientific interest". The zone must be more rugged and geologically diverse than ever known by the Viking lander or the Pathfinder.
The current images from MGS, obtained during an aerobraking orbit from about 2,800 km above the surface, resolve objects about 15 meters across. If it reaches its final mapping orbit early next year, at an average of 378 km above the surface, MGS's MOC narrow angle camera will be able to resolve ground features as small as 2 to 3 meters across, allowing views of objects as small as boulders or as subtle as sand dunes. After MGS has reached its final orbit, data from the spacecraft's laser altimeter, which measures the height and roughness of Martian surface features, will be combined with imaging data to aid the final choice of landing sites.

The MCO, like MGS, carries two cameras in a compact package about the size of a pair of binoculars. The Mars colour imager's 0.5-kg wide-angle camera will return daily low-resolution global views of Mars' atmosphere and surface, while its medium-angle camera will provide higher resolution (40 meters per pixel) images. The medium-angle camera will build global and regional maps of Mars in multiple colours over the course of the mission. These maps will be used to characterise surface properties and changes in the distribution of dust.

The MPL carries three scientific packages: the Mars descent imager, the atmospheric lidar experiment, coupled with a miniature microphone furnished to record the sounds of Mars and the Mars Volatile and Climate Surveyor package. The latter includes a surface stereo imager, a meteorology package, a robotic arm to acquire soil samples and close-up images of the surface and subsurface; and the thermal and evolved gas analysis experiment. The robotic arm, which is reminiscent of the Viking arm and scoop is much more versatile. It can reach farther out, dig up to 1 meter below the surface and then place soil samples in a miniature oven, called the evolved gas analysis experiment, where the samples are 'cooked' and analyzed for chemical and gas content.
MPL piggybacks two small, 2kg microprobes. Deployed before landing, they will penetrate and embed themselves beneath the Martian surface to study subsurface materials.

More detailed information will be obtained through the following Web-Sites:
http://www.msss.com/mars/surveyor/ms98.html
http://mars.jpl.nasa.gov/msp98/index.html

(Mk & Mn)

CMO Clicks (13) -Japanese-

　NASAの火星探査機に関する情報は次ののURLから辿れる。
　http://mpfwww.jpl.nasa.gov/

　マーズ・パスファインダーは、度々の地上からの呼びかけにも応答せず、機能の再起動は絶望的になり、1998年三月になって運用終了が宣言された。
　マーズ・グローバルサーヴェイヤーはエアロブレーキが中断され、1998年四月初めから撮影が再開された。九日おきの撮影計画 (3～5, 12～14, 21～23 April 1998) 等があり、画像処理が終わると、迅速に発表されている。以下のWerbSiteで各種の処理の画像を見ることが出来る。

　http://www.jpl.nasa.gov/marsnews
　http://mars.jpl.nasa.gov
　http://photojournal.jpl.nasa.gov

　1998年二月には、マーズ・サーヴェイヤー1998 の計画の発表があった。それによると、今回の科学テーマは"Volatiles and Climate History"とされ、前回のマーズ・パスファインダーとマーズ・グローバル・サーヴェイヤーによって得られる知識に加えて、現在の火星環境のより詳しい知見を手に入れるのが目的である。今回の探査機計画も別々に打ち上げられる軌道周回機と着陸機の組み合わせで、それぞれ、"Mars Climate Orbiter (MCO)"、"Mars Polar Lander (MPL)"と名付けられた。打ち上げと火星到着の予定は下記のように計画されている。前者は大気と地理、後者は地下の水(H₂O)や地勢、気候変化の物理的痕跡の探査などを目指す。

　残念なことに、火星に到着するのは次の観測期の終盤になってしまい、リアルタイムな我々の観測との照合にはあまり役立たない様に思われる。参考までに到着時のLsと地上からの視直径δを付加しておいた。


　　　　打ち上げ　　 　火星到着
MCO  10 Dec 1998  23 Sept 1999 (211ﾟLs, δ=7.1")
MPL　03 Jan 1999  03 Dec  1999 (256ﾟLs, δ=5.5")

　今度の着陸機は、南極近くの75ﾟS程の極地に軟着陸するが、場所の選定はこれからMGSなど結果などを総合して決定されるようである。着陸船のロボット・アームはヴァイキングのそれより優れていて一メートルも掘り、土壌サンプルを煎ってその化学的組成を調べる。また着陸機は小さな探査装置を二機背負っていて、着陸する前に地表の下を調べるために、火星表面に向けて打ち込まれるという。軌道周回船はMGS同様に、エアロブレーキで減速後に周回軌道に入り、大気現象と表面の様子を観測する計画になっている。カメラは小型だが二個積まれていて、広角は毎昼のグローバルな火星面像を送ってくるようである。

　The Mars Surveyor 1998 の詳しい計画については次のURLからも辿れる。
　　　 http://www.msss.com/mars/surveyor/ms98.html
　　　http://mars.jpl.nasa.gov/msp98/index.html

(Mk)

Back to the Façade / Back to the CMO Home Page