DSN Radio Astronomy
Milestones
These are some of the breakthroughs in radio astronomy which were
accomplished using the NASA Deep Space Network
| 1967 | First intercontinental very long baseline interferometry (VLBI) By combining the signals from distantly separated radio telescopes, fine details can be resolved in the structure of radio sources. The greater the separation, the finer the details. Prior to this, VLBI had been limited to telescopes in North America. |
| 1969 | Pulsar observations at 2295 MHz, highest frequency to date Using the Goldstone 64-m antenna at 13-cm wavelength allowed the polarization characteristics of a number of pulsars to be determined. At high frequencies, pulsar signals are less affected by the interstellar plasma through which they pass on their way to earth. |
| 1969 | First jump in the period of the Vela pulsar detected While monitoring the period of a set of pulsars with the Goldstone 64-m antenna, a sudden increase in the period of the Vela pulsar was detected. This was attributed to a settling of the matter of the neutron star, similar to an earthquake. |
| 1971 | Discovery of superluminal motions in 3C273 and 3C279 Comparing the images made at two different times using the VLBI technique (see 1967), it appeared as if matter in these objects was moving with greater than the speed of light. This is now understood as an illusion due to the orientation of the matter flow and the effect of special relativity. |
| 1973 | Best upper limit to date on cosmic background small-scale anisotropy
The currently clumpu distribution of matter in the universe, in stars and galaxies and clusters of galaxies, evolved from a very smooth initial distribution. Explaining this is still a challenge for cosmologists. |
| 1982 | Most distant quasar discovered with Tidbinbilla Interferometer
Using an interferometer consisting of two antennas at NASA's Canberra (Tidbinbilla) Complex, precise positions were determined for a large number of radio sources. This allowed them to be associated with optical objects which were then identified. One of them turned out to be the most distant quasar then known. |
| 1986 | First space-based VLBI with TDRSS antenna As a proof of concept, the DSN 70-m antennas were used with a NASA TDRSS (Tracking and Data Relay System Satellite) to make VLBI (see 1967) observations of three quasars. In addition to obtaining finer detail than ever before, this demonstrated that VLBI baselines could be larger than the diameter of the Earth. |
| 1991 | Measurement of the relativistic bending of radiation by Jupiter, providing an impressive confirmation of the theory of general relativity which avoided possible effects due to the solar corona present in typical measurements of this type. |
| 1992 | First speckle hologram of the interstellar plasma By using an array of southern hemisphere antennas, including two at NASA's Canberra Complex, and two former DSN antennas (Hartebeesthoek and Hobart) to observe the Vela pulsar, correlations in the time variation at the various stations were analyzed to obtain information about the structure of the interstellar plasma. |
| 1995 | First images of motion in the nearest active galactic nucleus By a series of VLBI observations over a period of eight years, using telescope arrays which included NASA 70-m antennas, jets of plasma were seen to flow out of the core of Centaurus A. The behavior of this core may be typical of other, more distant active galactic nuclei. |
| 1995 | First image of infall onto a protostar A protostar is a star which is still growing by accreting matter from the cloud out of which it formed. By combining data from the Goldstone 70-m with data from the Very Large Array (VLA), images were made of the material falling onto the protostar B335. Neither telescope by itself could produce such images. |
| 1996 | First evidence for the formation of a pre-protostellar core by
coagulation By combining Goldstone 70-m data with VLA data, and comparing the results with those obtained with other telescopes, the cloud core L1498 was found to be growing by accreting material. The cloud is not collapsing like B335 (see above) but may be growing towards a stage when collapse will occur. Before this, it was not known whether pre-stellar cores grew by slow accretion of surrounding material. |
| 1996 | Nano-arcsecond resolution of the Vela pulsar Further analysis of the speckle data obtained in 1992 (see above) allowed interstellar scattering to be used to determine the size (approximately 500 km) and approximate shape of the emitting region of the Vela pulsar. |
| 1997 | First VLBI astrometric detection of an unseen companion of a star
The 70-m antenna at NASA's Canberra Complex was combined with the ex-DSN antenna at Hobart and the 64-m telescope at Parkes to make precise measurements of the position of the star AB Doradus. A wobbling in the position of the star revealed the presence of a dark companion with about a tenth the mass of the sun. |
| 1997 | First images from the HALCA Space VLBI mission The Japanese HALCA space telescope is the first dedicated orbiting VLBI antenna. Its orbit was chosen to provide the longest baselines to date. The NASA 70-m antennas, because of their size and geographic locations, play an important role in producing sensitive and detailed images of compact radio sources. |