Julian day number is the number of days since __________

December 1, 1900

January 1, 2000

December 1, 4713 BC

January 1, 4713 BC

Correct Answer : January 1, 4713 BC

Explanation : The Julian day number is the number of days since the noon on January 1, 4713 BC as per Universal Time. It counts the days elapsed since the mentioned date & finds use in astronomy and software purposes. Julian Day Number (JDN) is an integer value denoting each solar day passed.

Recently Updated in Spaceflight Mechanics Questions

What are the disadvantages of the optical sensors?

They are not efficient

Weather must be favorable

They are not accurate

Satellite must be in darkness

Correct Answer : Option (B) : Weather must be favorable

Explanation : The optical sensors are very accurate in determining the satellite. For taking a good photo, there are some conditions that have to be followed- good weather conditions, correct lighting and the satellite must be in the sunlight.

Which of these devices is used to observe objects by having two or more antennas with high aperture?

Telescope

Hyper telescope

Radio interferometer

Optical Interferometer

Correct Answer : Option (C) : Radio interferometer

Explanation : Radio interferometers are sensors which accurately measure the directional information of a satellite using radio interferometry. It makes use of 2 or more antennas of high aperture and waves interferes on the same receiver. This is similar to the double- slit experiment phenomenon.

Which of these radars operate by identifying signature od a booster by disturbance in ionosphere?

Pulse radar

Surface radar

Continuous wave radar

Over- the- horizon radar

Correct Answer : Option (D) : Over- the- horizon radar

Explanation : OTH radar operates on the principle of detecting launches and identifying the signature of a particular booster by the disturbance it causes in the ionosphere.