CelesTrak: A New Way to Obtain GP Data

submited by

Style Pass

2021-07-26 14:00:04

The US government has provided GP or general perturbations orbital data to the rest of the world since the 1970s. These data are produced by fitting observations from the US Space Surveillance Network (SSN) to produce Brouwer mean elements using the SGP4 or Simplified General Perturbations 4 orbit propagator.

Many of you are familiar with this data in the form of TLEs or Two-Line Element Sets. TLEs were designed to provide the minimum data necessary to propagate the orbit of a resident space object (RSO) at a time when both bandwidth for transmission or digital storage were extremely limited. In fact, at the time, transmission might be via fax, hard copy (postal delivery), or even read over the phone and storage was handled using punch cards or magnetic tape.

While this format has served us well for many decades, it has not been without its share of problems. For example, the choice of a two-digit year caused many problems approaching Y2K—problems that were side-stepped by redefining what those two digits represented—but that Y2K problem persists fully 20 years into the 21st century. And now we are approaching another milestone where we will no longer be able to catalog all the objects we track within the 5-digit catalog number limitation of the TLE format.