Get fully defined orbit from space-track.org SATCAT

Question

My question is related to this one on Physics SE. Admittedly, I'm somewhat preempting the answer over there being "you can't, there's a missing parameter", so if it comes back that you can derive this parameter mathematically, I'll close this question.

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The space-track.org API returns a model conforming to this from the /basicspacedata/modeldef/class/satcat endpoint:

{
  "controller": "basicspacedata",
  "data": [
    {
      "Field": "INTLDES",
      "Type": "char(12)",
      "Null": "NO",
      "Key": "",
      "Default": "",
      "Extra": ""
    },
    {
      "Field": "NORAD_CAT_ID",
      "Type": "int(10) unsigned",
      "Null": "YES",
      "Key": "",
      "Default": null,
      "Extra": ""
    },
    {
      "Field": "OBJECT_TYPE",
      "Type": "varchar(12)",
      "Null": "YES",
      "Key": "",
      "Default": null,
      "Extra": ""
    },
    {
      "Field": "SATNAME",
      "Type": "char(25)",
      "Null": "NO",
      "Key": "",
      "Default": "",
      "Extra": ""
    },
    {
      "Field": "COUNTRY",
      "Type": "char(6)",
      "Null": "NO",
      "Key": "",
      "Default": "",
      "Extra": ""
    },
    {
      "Field": "LAUNCH",
      "Type": "date",
      "Null": "YES",
      "Key": "",
      "Default": null,
      "Extra": ""
    },
    {
      "Field": "SITE",
      "Type": "char(5)",
      "Null": "YES",
      "Key": "",
      "Default": null,
      "Extra": ""
    },
    {
      "Field": "DECAY",
      "Type": "date",
      "Null": "YES",
      "Key": "",
      "Default": null,
      "Extra": ""
    },
    {
      "Field": "PERIOD",
      "Type": "decimal(12,2)",
      "Null": "YES",
      "Key": "",
      "Default": null,
      "Extra": ""
    },
    {
      "Field": "INCLINATION",
      "Type": "decimal(12,2)",
      "Null": "YES",
      "Key": "",
      "Default": null,
      "Extra": ""
    },
    {
      "Field": "APOGEE",
      "Type": "bigint(10) unsigned",
      "Null": "YES",
      "Key": "",
      "Default": null,
      "Extra": ""
    },
    {
      "Field": "PERIGEE",
      "Type": "bigint(10) unsigned",
      "Null": "YES",
      "Key": "",
      "Default": null,
      "Extra": ""
    },
    {
      "Field": "COMMENT",
      "Type": "char(32)",
      "Null": "YES",
      "Key": "",
      "Default": null,
      "Extra": ""
    },
    {
      "Field": "COMMENTCODE",
      "Type": "tinyint(3) unsigned",
      "Null": "YES",
      "Key": "",
      "Default": null,
      "Extra": ""
    },
    {
      "Field": "RCSVALUE",
      "Type": "int(1)",
      "Null": "NO",
      "Key": "",
      "Default": "0",
      "Extra": ""
    },
    {
      "Field": "RCS_SIZE",
      "Type": "varchar(6)",
      "Null": "YES",
      "Key": "",
      "Default": null,
      "Extra": ""
    },
    {
      "Field": "FILE",
      "Type": "smallint(5) unsigned",
      "Null": "NO",
      "Key": "",
      "Default": "0",
      "Extra": ""
    },
    {
      "Field": "LAUNCH_YEAR",
      "Type": "smallint(5) unsigned",
      "Null": "NO",
      "Key": "",
      "Default": "0",
      "Extra": ""
    },
    {
      "Field": "LAUNCH_NUM",
      "Type": "smallint(5) unsigned",
      "Null": "NO",
      "Key": "",
      "Default": "0",
      "Extra": ""
    },
    {
      "Field": "LAUNCH_PIECE",
      "Type": "varchar(3)",
      "Null": "NO",
      "Key": "",
      "Default": "",
      "Extra": ""
    },
    {
      "Field": "CURRENT",
      "Type": "enum('Y','N')",
      "Null": "NO",
      "Key": "",
      "Default": "N",
      "Extra": ""
    },
    {
      "Field": "OBJECT_NAME",
      "Type": "char(25)",
      "Null": "NO",
      "Key": "",
      "Default": "",
      "Extra": ""
    },
    {
      "Field": "OBJECT_ID",
      "Type": "char(12)",
      "Null": "NO",
      "Key": "",
      "Default": "",
      "Extra": ""
    },
    {
      "Field": "OBJECT_NUMBER",
      "Type": "int(10) unsigned",
      "Null": "YES",
      "Key": "",
      "Default": null,
      "Extra": ""
    }
  ]
}

In terms of fields that relate to the orbit of the satellite, I make it:

• Period
• Inclination
• Apogee
• Perigee

Which is all great information. However, I want to be able to fully define these orbits in terms of the classical Keplerian representation used by the ESA such that I can compare data from the two. To do this, I somehow need to find the right ascension of the ascending node / longitude of the ascending node.

Now, I'm assuming that space-track has this information somewhere... It seems somewhat pointless to miss a key parameter out of an orbital definition. So where can I find it?

Answer 1

Problem 1: you're querying the wrong database. For orbit data, you don't want SATCAT, you want ELSETs, which means you need to use "gp" (for General Perturbations) in your URL in place of "satcat".

Problem 2: the values you retrieve through the gp URL must be used with great care. They are NOT osculating elements that everyone understands. They are a particular type of mean elements, which have been mangled by mathematics into something that uses the same words to mean completely different things. I strongly recommend reading the following links for warnings of the kinds of things that go wrong all too easily.

The bottom line is, if at all possible, use TLEs only as inputs to SGP4 (which is also downloadable from space-track.org), tell SGP4 to compute J2000 position and velocity, and use some other tool to operate on those values.

Confused about SGP4 implementation published by celestrack

Mean to Osculating conversion for non-J2 averaged elements

Python orbit simulation using TLE-tools and poliastro

Failing at getting apogee and perigee from TLE

How is an input card for SGP4/other astro standards packages crafted?

Has Skyfield or any other SGP4-capable open-source Python package yet wrapped/implemented the new, improved SGP4 (version 8+)?