Mission to Mars!

Here we use the <A ...> </A> "anchor, end-anchor" construction to define a reference spot or label in this html document. The actual name of the label is specified by the "NAME = ..." part of this. Note that the "NAME = ..." statement IS case-sensitive, so that "contents" and "Contents" would be two different labels. Labels are used to mark locations in documents for the purpose of being able to define hypertext links to those locations.

Links that jump to another place in the same document

The Mars Global Surveyor

MGS: News overview
MGS spacecraft schematic
Other links to learn more about MGS

Each of the previous 3 lines produces a line of "clickable text" in the window displayed by the browser. This construction is the basis of hypertext links. The <A ...> tag is an "anchor" tag, and that command is finished off by the </A> "end - anchor" command. Whatever appears between the <A> and the </A> tags is a hypertext link, meaning that it is "clickable". In the first case above, for example, the words "MGS: News overview" are clickable, because that phrase is between the tags. (Note that the clickable thing could be an image, for example, by having something like <img src = "myimage.gif"> replace the text phrase between the tags. This is illustrated in the next example.)

The result of clicking is to take the user to the location specified in the <A HREF = ...> part of the tag. The "HREF = " specifies the "hypertext reference" -- the location to which the browser should go when the user clicks the link. In each of the cases above, the HREF specifies a location which is a label within the current document. The "#" symbol used in the "HREF = ..." statement indicates that the label which follows refers to a location within the document. (Note: To go to a specific location within ANOTHER document, one would use an <A HREF = docname.htm#label> type of tag.)

Small images which can be clicked to view larger versions

Links that jump to another document on the same computer

The Mars Global Surveyor mission, undertaken by NASA this past Thursday, is a perfect illustration of the physics you have been studying these past weeks. Space missions combine all the most recent advances in physics and technology: mechanics, materials sciences, electronics, computing, optics, and more.

The following two link examples use "clickable images" to provide the hypertext links. Clicking on one of these small images causes another (larger version) image to be displayed by the browser. The larger images are files which are in the "152gif" subdirectory of this computer. (Note: This is sometimes a useful way to show a lot of images on one page and still keep the document load/display time down. The smaller version images are often called "thumbnail" images.)

The MGS probe will leave the (blue) Earth orbit and move along the (yellow) transfer orbit until it reaches the (red) martian orbit next fall. All this time the probe is orbiting the Sun.

Click on the orbit transfer picture on the left to see a larger image of the orbit transfer with the relevant physics data.

1. What would be the speed of the MGS probe if it were to stay in the same orbit as the Earth (the blue orbit in the picture?) Note the position of Mars as the probe starts on its journey towards it.

Once the probe reaches its destination orbit it will be shifted into an orbit around Mars (the "capture orbit" drawn in yellow.) This is the MOI (Mars Orbit Insertion) phase of the mission. Click on the MOI picture on the right to access the larger MOI picture with the relevant physics data.

Click here if you would like to see the original page from which this excerpt comes.

This link example links to another html document rather than to an image file. The html file is in the same directory as this document.

Back to the top of this document

This link takes us back to the label "top" in THIS document. Recall that this label was defined up near the top of this document in the <A NAME = "top"></A> tags.

< BR>

Here is the "overview" label location. Any link to #overview will come here.

MGS: A Brief Overview, with credits to CNN...

On Thursday, 7 Nov 1996, NASA launched a 10-month, unmanned mission to Mars, the first step in a multi-spacecraft bid to determine if there is -- or ever was -- life on the fourth rock from the sun.

Global Surveyor, the first of 10 NASA probes bound for Mars the next decade, replaces one that mysteriously disappeared three years ago.

Surveyor will take 10 months to make the 470-million-mile trip and another six months to ease into a mapping orbit. Later, it will dip into the Red Planet's thin atmosphere, using its wing-like solar panels as brakes.

Surveyor will study the Martian surface and atmosphere, but will not land.

Back to the Table of Contents

This link takes us back to the "contents" label in the first link example near the top of this document.

< BR>
Here is the "schematic" label location. Any link to #schematic will come here.

Here is a schematic of the Mars Global Surveyor, courtesy of NASA:

Back to the Table of Contents

< BR>
Here is the "other" label location. Any link to #other will come here.

Links to another (http://) location

Further MGS study links:

The hypertext reference specified need not be a file on the current computer. It can also be specified as a "hypertext transmission protocol [http]" address or location, just like the addresses (URLs) you can type into the browser location field. The following four examples go to external WWW sites, where LOTS of fascinating information about the Mars Global Surveyor can be found. You can point your students directly to external sites in this way.

1. 2. 3. 4.

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