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Landing at Lunar Sunrise: A Mission Planning Briefing

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Landing at Lunar Sunrise: A Mission Planning Briefing

Use a lamp-and-ball model to plan sunlight, eclipses and seasons for a Moon lander.

Part 1: Phases and sunlight at the landing site

Read the briefing notes and Table 1, then answer questions 1 to 4.

Briefing Day: When to Land

1Adaeze Lindqvist, an eighth grader, spent a summer day at a space agency's mission center for students. She sat in on a planning briefing for a small robotic lander that will touch down on the Moon's near side, the side that always faces Earth. The landing site is near the middle of the near side, close to the Moon's equator. The lander runs on solar panels, with a battery for short dark spells.

2The planner, Ms. Ruth Nakashima, explained that the Moon has day and night just as Earth does, but a lunar day is much longer. In one cycle of phases, about 29.5 Earth days, each place on the Moon goes from one sunrise to the next. Daylight lasts for about half of the cycle and night for the other half. At the landing site, the ground heats to over 100 °C around noon and cools below −170 °C at night. The lander is not built to survive the night, so its work will end at sunset.

3To plan the landing day, Ms. Nakashima used a model. A lamp stood for the Sun, Adaeze's head for Earth, and a foam ball on a stick for the Moon. A sticker on the ball marked the landing site, and Adaeze kept the sticker facing her head as she moved the ball in a circle around herself. The lamp always lit the half of the ball that faced it. Adaeze watched the ball go through its phases and checked whether the sticker sat in the lit half or the dark half.

4The team wants to land soon after sunrise at the site. A low Sun casts long shadows, which make rocks and holes easy to spot during landing, and an early landing leaves the most daylight for science work. The team also checked the forecast for eclipses during the mission. Without sunlight, the lander uses 100 W of power, and its battery stores 600 Wh. During the lunar eclipse in Table 1, Earth's shadow will cover the landing site for about 3.5 hours.

5A second team is planning a lander for a site directly opposite this one, in the middle of the far side, which never faces Earth. That lander will send its radio signals through a satellite that circles the Moon. Ms. Nakashima also compared the Moon with Earth. The Moon travels around the Sun along with Earth, so both stay about the same distance from the Sun. Earth's axis is tilted about 23.5°, while the Moon's axis is tilted only about 1.5°.

Table 1: Mission Calendar for One Cycle of Phases
Mission dayPhase seen from EarthPlanned event
0New moon—
7First quarter—
15Full moonLunar eclipse
22Third quarter—
29.5New moonSolar eclipse seen from parts of Earth
1.
Use the model in paragraph 3. The sticker always faces Earth, and the phases go in the order shown in Table 1. Match each phase seen from Earth to the time of day at the landing site.
2.
Use paragraph 4 and your answers to question 1. Which landing time fits the team's plan best?
Question 2 options
3.
Use Table 1 and your answers to question 1. The lander touches down on day 8 and stops working at sunset at the site.

The lander will have about Earth days of daylight to work.

4.
Use paragraphs 2 and 3. Why is one day at the landing site so much longer than one day on Earth?
Question 4 options

Part 2: Eclipses and the far side

Use paragraphs 4 and 5, Table 1 and the model to answer questions 5 to 8.

5.
Use paragraph 4.

With no sunlight, a full battery can run the lander for hours. That leaves about hours to spare after the eclipse darkness ends.

6.
Why will the lunar eclipse on day 15 darken the landing site?
Question 6 options
7.
Does the near-side team need a plan for the solar eclipse on day 29.5?
Question 7 options
8.
Use paragraph 5 and the model. Sort each statement by the site it is true for.

Part 3: Tilt and seasons

Use Table 2 and paragraph 5 to answer questions 9 and 10. Then use the whole page for question 11.

Table 2: Noon Sun Height at 40° North During One Trip Around the Sun
WorldHighest noon SunLowest noon Sun
Earth73.5°26.5°
Moon51.5°48.5°
9.
Use Table 2. Find how much the noon Sun height changes in a year on each world.

On Earth, the noon Sun height changes by °. On the Moon, it changes by °.

10.
A place at 40° north on Earth has strong seasons, but a place at 40° north on the Moon has almost none. Which explanation fits Table 2 and paragraph 5 best?
Question 10 options
11.
A reporter at the briefing asks, "Why not land at full moon, when the site gets the most sunlight?" Write a claim that answers the reporter. Use evidence from Table 1, paragraph 4 and the model, and explain your reasoning.