On the way back to Earth, Al Worden took the very first deep-space walk - at what was then the record distance of 315,000 kilometers (196,000 miles) from Earth - retrieving film cassettes from the panoramic and mapping cameras from the rear of a

subsatellite that they had sent into orbit two days previously: "I spent 38 minutes working in the vacuum of space, getting a perfect view of both my home planet and the Moon at the same time," explained Al Worden.

Each scan spot covers a 9-km square on the Earth's surface along the

subsatellite track.

A small camera

subsatellite will watch the cratering process unfold from about a kilometer way in space, taking an image every second for later downlink to Earth while the mother ship hides behind Ryugu.

The temporal order of

subsatellite trackes is illustrated in Figure 2.

Later, in 1977, a point-mass representation of the quasi-global gravity field of the Moon, consisting of 117 distributed point masses, was developed by processing the Apollo 15 and 16

subsatellite and LO-V radio tracking data [27].

The aim of this paper is to reveal the impact dynamics of a tethered

subsatellite system under tether constraint.

where [phi] is the latitude of the destination, [lambda] = [[lambda].sub.sat] - [[lambda].sub.des] is the longitude difference between the

subsatellite point and the ground station, [[lambda].sub.sat] represents the longitude of

subsatellite point, [[lambda].sub.des] is the longitude of destination, [DELTA] [phi] is the drift of satellite in the northsouth direction, and [DELTA] [lambda] is the drift of satellite in the eastwest direction.

where m is the number of CCD valid elements, n is the number of quantization bits, [f.sub.L] is the push-broom line frequency, f is the focus of space cameras, H is the average height of satellite orbit, V is the

subsatellite point velocity, and a is the CCD pixel size.

When [omega] = [pi]/2 or 3[pi]/2, i = 2e, it yields [([lambda] - [[lambda].sub.0]).sup.2] + ([[phi].sup.2] [approximately equal to] [i.sup.2] and the

subsatellite ground track is approximately a circle.

This instrument and its

subsatellite will make coordinated observations with the agency's Tail Probe, launched last August to explore the cometlike tail of Earth's magnetosphere.

Once the

subsatellite path meets the equatorial plane the ascending node N location can be identified.

The view coverage of EOS can be formed on the ground by the

subsatellite point of satellite platform as well as the view angle, swing angle, and tilting angle of satellite payload [12-14].