Geomagnetic disturbances can be monitored by ground-based magnetic observatories recording the three magnetic field components. The global Kp index is obtained as the mean value of the disturbance levels in the two horizontal field components, observed at 13 selected, subauroral stations . ... Geomagnetic activity is the occurrence of K variations. ... But K still remains a local index, describing disturbances in the vicinity of each observatory. ...

... Mass . ... Following several successful moon landings,NASA decided to use its last Saturn V not to fly to the moon but to place in low Earth orbit a large space station, named Skylab. ... It was followed that year by three manned flights using the smaller Saturn IB, each carrying 3 astronauts for a prolonged stay aboard Skylab. ... Mass measurements aboard Skylab were part of the medical experiments conducted there. ... Measuring body mass in the M172 chair (see illustration) was not a simple matter...