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qianniu
sage

Reged: 05/05/07

Loc: Columbus, OH
NASA Spacecraft Database
#5428091 - 09/18/12 07:22 PM
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Hi,

While searching for satellite database on the web, I found that NASA has a rather comprehensive spacecraft database that is searchable by the public.

http://nssdc.gsfc.nasa.gov/nmc/SpacecraftQuery.jsp

For most of the objects, trajectory details are also provided. One example:

Periapsis Apoapsis Period Inclination Eccentricity
505.0 km 550.0 km 95.19999694824219 minutes 74.0° 0.0032560001127421856

I am still trying to learn the basics of orbit parameters through Wikipedia,

http://en.wikipedia.org/wiki/Orbital_elements

It seems to me that NASA's parameters missed the Longitude of Ascending Node, and the Argument of Periapsis. So shape is unambiguously defined, but not orientation.

What did I miss here?

Thanks!

Qianniu

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WarmWeatherGuy
Pooh-Bah

Reged: 08/27/11

Loc: Orlando, FL 28° N, 81° W
Re: NASA Spacecraft Database [Re: qianniu]
#5432259 - 09/21/12 08:31 AM
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You also need to know a time when the satellite was at periapsis (or the mean anomaly at some epoch). This allows you to compute the mean anomaly which then allows you to compute the eccentric anomaly which then allows you to compute the true anomaly. The true anomaly is the angle between periapsis to the satellite in the plane of the orbit.

Edit: fixed spelling

Edited by WarmWeatherGuy (09/24/12 02:23 AM)

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qianniu
sage

Reged: 05/05/07

Loc: Columbus, OH
Re: NASA Spacecraft Database [Re: WarmWeatherGuy]
#5436877 - 09/23/12 08:03 PM
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Thanks WarmWeather for pointing this out. I am just a little disappointed why NASA provides an incomplete picture of the orbit.

Do you know of any other resources for better data of the satellites? Given the fact that there are multiple websites with live satellite tracking services, there must be such resources. Though for my little toy research project, I'll need complete trajectory information on all the earliest satellites that are no longer circulating the planet Earth.

Thanks!

qianniu

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WarmWeatherGuy
Pooh-Bah

Reged: 08/27/11

Loc: Orlando, FL 28° N, 81° W
Re: NASA Spacecraft Database [Re: qianniu]
#5436908 - 09/23/12 08:18 PM
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You can get enough data here to spot the satellites. I wrote a program years ago on my TRS-80 (in BASIC) that allowed me to predict when a satellite would appear. It worked!

I started a company called Mr. Orbit that sold customized satellite predictions for a month. They had to be customized because they are different for each city. They could only be good for a month because the orbits decay too much to accurately predict where a satellite will be more than a month in advance. At least for the satellites that are in very low Earth orbit, the ones that are the brightest.

You can understand what the numbers mean in the two-line orbital elements here.

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WarmWeatherGuy
Pooh-Bah

Reged: 08/27/11

Loc: Orlando, FL 28° N, 81° W
Re: NASA Spacecraft Database [Re: WarmWeatherGuy]
#5437389 - 09/24/12 02:32 AM
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If you want orbital elements of some satellites that are no longer up you should buy this book on Amazon.

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