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If you are looking for something "at" L4 or L5, the news is that these are not really points (since Earth's orbit is not a perfect circle) as much as they are regions, neighborhoods, or states of mind. It's better to thing of things as orbiting around the Lagrange points (any of them) than being at them.

Getting to the neighborhood would not be a problem. The two STEREO spacecraft passed near the neighborhood of Earth's L4 and L5, and slowing down enough to enter an orbit around the L4/L5 libration points would have required a significant additional delta-v but one that would be small compared to that of getting there from Earth in the first place.

According to Wikipedia:

As they passed through Earth's Lagrangian points L4 and L5, in late 2009, they searched for Lagrangian (trojan) asteroids.

Here's a plot of data I downloaded from JPL Horizons, showing the approximate distance from the Sun (actually the cm of the solar system) of STEREO-A, STEREO-B, and Earth (lower, upper, and middle (blue, green, red) traces respectively) and the lead/lag angle of the two STEREO spacecraft with respect to the earth (actually the differences in theta = arctan2(y, x) in J2000 ecliptic coordinates). +/- 60 degrees is indicated by dotted lines.

They did use several flyby's of the Moon in a rather cool maneuver to get into this situation (GIF from that answer) - one orbiting the Sun in a retrograde direction. Doing that without the moon would have been quite difficult = expensive in delta-v!

The canonical answers to "why didn't they..." are always about less-than-limitless funding and scientific prioritization. Without a compelling reason to go to Earth's L4/L5 and not do something else, it won't happen. See @AndrewThompson's comment for further insight.

Now here's a nice video of the two Stereo spacecraft passing through the neighborhood of Earths' L4/L5 (not labeled, at +/- 60 degrees from the Earth); enjoy!

If you are looking for something "at" L4 or L5, the news is that these are not really points (since Earth's orbit is not a perfect circle) as much as they are regions, neighborhoods, or states of mind. It's better to thing of things as orbiting around the Lagrange points (any of them) than being at them. This means that if there is stuff to look at, but you don't know exactly where it is in those orbits, you'd never get very close to it because these neighborhoods are huge!

Getting to the neighborhood would not be a problem. The two STEREO spacecraft passed near the neighborhood of Earth's L4 and L5, and slowing down enough to enter an orbit around the L4/L5 libration points would have required a significant additional delta-v but one that would be small compared to that of getting there from Earth in the first place.

According to Wikipedia:

As they passed through Earth's Lagrangian points L4 and L5, in late 2009, they searched for Lagrangian (trojan) asteroids.

Here's a plot of data I downloaded from JPL Horizons, showing the approximate distance from the Sun (actually the cm of the solar system) of STEREO-A, STEREO-B, and Earth (lower, upper, and middle (blue, green, red) traces respectively) and the lead/lag angle of the two STEREO spacecraft with respect to the earth (actually the differences in theta = arctan2(y, x) in J2000 ecliptic coordinates). +/- 60 degrees is indicated by dotted lines.

They did use several flyby's of the Moon in a rather cool maneuver to get into this situation (GIF from that answer) - one orbiting the Sun in a retrograde direction. Doing that without the moon would have been quite difficult = expensive in delta-v!

The canonical answers to "why didn't they..." are always about less-than-limitless funding and scientific prioritization. Without a compelling reason to go to Earth's L4/L5 and not do something else, it won't happen. See @AndrewThompson's comment for further insight.

Now here's a nice video of the two Stereo spacecraft passing through the neighborhood of Earths' L4/L5 (not labeled, at +/- 60 degrees from the Earth); enjoy!

Getting there would not be a problem. The two STEREO spacecraft passed near the neighborhood of Earth's L4 and L5, and slowing down enough to enter an orbit around the L4/L5 libration points would have required a significant additional delta-v but one that would be small compared to that of getting there from Earth in the first place.

According to Wikipedia:

As they passed through Earth's Lagrangian points L4 and L5, in late 2009, they searched for Lagrangian (trojan) asteroids.

Here's a plot of data I downloaded from JPL Horizons, showing the approximate distance from the Sun (actually the cm of the solar system) of STEREO-A, STEREO-B, and Earth (lower, upper, and middle (blue, green, red) traces respectively) and the lead/lag angle of the two STEREO spacecraft with respect to the earth (actually the differences in theta = arctan2(y, x) in J2000 ecliptic coordinates). +/- 60 degrees is indicated by dotted lines.

They did use several flyby's of the Moon in a rather cool maneuver to get into this situation (GIF from that answer) - one orbiting the Sun in a retrograde direction. Doing that without the moon would have been quite difficult = expensive in delta-v!

The canonical answers to "why didn't they..." are always about less-than-limitless funding and scientific prioritization. Without a compelling reason to go to Earth's L4/L5 and not do something else, it won't happen. See @AndrewThompson's comment for further insight.

Now here's a nice video of the two Stereo spacecraft passing through the neighborhood of Earths' L4/L5 (not labeled, at +/- 60 degrees from the Earth); enjoy!

If you are looking for something "at" L4 or L5, the news is that these are not really points (since Earth's orbit is not a perfect circle) as much as they are regions, neighborhoods, or states of mind. It's better to thing of things as orbiting around the Lagrange points (any of them) than being at them.

Getting to the neighborhood would not be a problem. The two STEREO spacecraft passed near the neighborhood of Earth's L4 and L5, and slowing down enough to enter an orbit around the L4/L5 libration points would have required a significant additional delta-v but one that would be small compared to that of getting there from Earth in the first place.

According to Wikipedia:

As they passed through Earth's Lagrangian points L4 and L5, in late 2009, they searched for Lagrangian (trojan) asteroids.

Here's a plot of data I downloaded from JPL Horizons, showing the approximate distance from the Sun (actually the cm of the solar system) of STEREO-A, STEREO-B, and Earth (lower, upper, and middle (blue, green, red) traces respectively) and the lead/lag angle of the two STEREO spacecraft with respect to the earth (actually the differences in theta = arctan2(y, x) in J2000 ecliptic coordinates). +/- 60 degrees is indicated by dotted lines.

They did use several flyby's of the Moon in a rather cool maneuver to get into this situation (GIF from that answer) - one orbiting the Sun in a retrograde direction. Doing that without the moon would have been quite difficult = expensive in delta-v!

The canonical answers to "why didn't they..." are always about less-than-limitless funding and scientific prioritization. Without a compelling reason to go to Earth's L4/L5 and not do something else, it won't happen. See @AndrewThompson's comment for further insight.

Now here's a nice video of the two Stereo spacecraft passing through the neighborhood of Earths' L4/L5 (not labeled, at +/- 60 degrees from the Earth); enjoy!

Getting there would not be a problem. The two STEREO spacecraft passed near the neighborhood of Earth's L4 and L5, and slowing down enough to enter an orbit around the L4/L5 libration points would have required a significant additional delta-v but one that would be small compared to that of getting there from Earth in the first place.

They did use several flyby's of the Moon in a rather cool maneuver to get into this situation (GIF from that answer) - one orbiting the Sun in a retrograde direction. Doing that without the moon would have been quite difficult = expensive in delta-v!

The canonical answers to "why didn't they..." are always about less-than-limitless funding and scientific prioritization. Without a compelling reason to go to Earth's L4/L5 and not do something else, it won't happen. See @AndrewThompson's comment for further insight.

Now here's a nice video of the two Stereo spacecraft passing through the neighborhood of Earths' L4/L5 (not labeled, at +/- 60 degrees from the Earth); enjoy!

Getting there would not be a problem. The two STEREO spacecraft passed near the neighborhood of Earth's L4 and L5, and slowing down enough to enter an orbit around the L4/L5 libration points would have required a significant additional delta-v but one that would be small compared to that of getting there from Earth in the first place.

According to Wikipedia:

As they passed through Earth's Lagrangian points L4 and L5, in late 2009, they searched for Lagrangian (trojan) asteroids.

Here's a plot of data I downloaded from JPL Horizons, showing the approximate distance from the Sun (actually the cm of the solar system) of STEREO-A, STEREO-B, and Earth (lower, upper, and middle (blue, green, red) traces respectively) and the lead/lag angle of the two STEREO spacecraft with respect to the earth (actually the differences in theta = arctan2(y, x) in J2000 ecliptic coordinates). +/- 60 degrees is indicated by dotted lines.

They did use several flyby's of the Moon in a rather cool maneuver to get into this situation (GIF from that answer) - one orbiting the Sun in a retrograde direction. Doing that without the moon would have been quite difficult = expensive in delta-v!

The canonical answers to "why didn't they..." are always about less-than-limitless funding and scientific prioritization. Without a compelling reason to go to Earth's L4/L5 and not do something else, it won't happen. See @AndrewThompson's comment for further insight.

Now here's a nice video of the two Stereo spacecraft passing through the neighborhood of Earths' L4/L5 (not labeled, at +/- 60 degrees from the Earth); enjoy!