<p>Like most asteroids and comets, 1I/'Oumuamua's trajectory was determined entirely by measuring its position in optical images over several days.
The earliest data came from automated, ground-based surveys such as Pan-STARRS and the Catalina Sky Survey,
then targeted follow-ups from various other asteroid observers.
The object's evident extrasolar origin motivated additional observations with more sensitive instruments including the Hubble Space Telescope.
'Oumuamua did not pass near enough to the Earth for a radar observation.</p>
<p>The Minor Planet Center collects those <a href="https://minorplanetcenter.net/db_search/show_object?object_id=1I" rel="nofollow noreferrer">observations here</a>.
In the table of orbital elements, the 0.4 arcsecond residual is the root-mean-square difference between positions computed using those elements and positions actually observed.
In the observation table, the magnitude column indicates which <a href="https://en.wikipedia.org/wiki/Photometric_system" rel="nofollow noreferrer">photometric filter</a> was used, e.g. G or R for greenish or reddish bands of visible light.
Pan-STARRS filter w passes a wide band including most of the visible band and some near infrared (<a href="https://ui.adsabs.harvard.edu/abs/2012ApJ...750...99T/abstract" rel="nofollow noreferrer">Tonry et al. 2012</a> table 4).</p>
<p><a href="https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=1I" rel="nofollow noreferrer">JPL's estimate</a> of 'Oumuamua's orbital elements uses the same observations and includes uncertainties.
They estimate about 1000 km error in perihelion distance (q), 23 seconds error in perihelion time (t<sub>p</sub>), and 1 arcsecond error in inclination (i) and ascending node longitude (node).
If you follow the Ephemeris link from there, and specify</p>
<p>Ephemeris Type: <strong>VECTORS</strong>
<br/>Table Settings: quantities code=<strong>2x</strong></p>
<p>then HORIZONS gives Cartesian position and velocity uncertainties based on dynamical simulation.
These are larger now than when it was observed, and still larger a few months before discovery.</p>

CC BY-SA 4.0
2020-10-09T03:16:02.300Z
OK. The answer is quite clear now.
Mahen
CC BY-SA 4.0
2020-10-08T20:02:47.753Z
2020-10-08T20:02:47.753Z
Mike G
<p>What measurements helped scientists understand 'Oumuamua's location and speed? I wanted to know how it was achieved and with what accuracy if possible.</p>

CC BY-SA 4.0
2020-10-01T17:14:21.737Z
Does this answer your question? [How did astronomers determine the path of 'Oumuamua so quickly?](https://astronomy.stackexchange.com/questions/26517/how-did-astronomers-determine-the-path-of-oumuamua-so-quickly)
Mike G
CC BY-SA 4.0
2020-10-02T05:57:09.697Z
@MikeG it talks about number of observations, but does not talk about how and what system was used. Is it taken for granted that Radar system is used. Plz correct me if I am wrong.
Mahen
CC BY-SA 4.0
2020-10-02T12:49:30.063Z
There was no radar observation, only optical astrometry.
Mike G
CC BY-SA 4.0
2020-10-04T01:06:27.360Z
Let's keep this question **open** and not prevent a good answer from being posted! (the proposed duplicate simply does not answer this question, it's a "sounds similar" question, perhaps selected hastily)
uhoh
<observational-astronomy><astrophysics><positional-astronomy><astrometry>
What measurements helped us in understanding 'Oumuamua's location and speed?
Mahen
# What measurements helped us in understanding 'Oumuamua's location and speed?

(Asked by: username_0 on 2020-10-01)

What measurements helped scientists understand 'Oumuamua's location and speed? I wanted to know how it was achieved and with what accuracy if possible.

**Tags:** observational-astronomy, astrophysics, positional-astronomy, astrometry
> **Comments:**
> **username_1**: Does this answer your question? [How did astronomers determine the path of 'Oumuamua so quickly?](https://astronomy.stackexchange.com/questions/26517/how-did-astronomers-determine-the-path-of-oumuamua-so-quickly)  
> **username_0**: @MikeG it talks about number of observations, but does not talk about how and what system was used. Is it taken for granted that Radar system is used. Plz correct me if I am wrong.  
> **username_1**: There was no radar observation, only optical astrometry.  
> **username_2**: Let's keep this question **open** and not prevent a good answer from being posted! (the proposed duplicate simply does not answer this question, it's a "sounds similar" question, perhaps selected hastily)  

---

## 1 answers

### Answer by username_1 on 2020-10-08. Score: 4 | Accepted answer

Like most asteroids and comets, 1I/'Oumuamua's trajectory was determined entirely by measuring its position in optical images over several days.
The earliest data came from automated, ground-based surveys such as Pan-STARRS and the Catalina Sky Survey,
then targeted follow-ups from various other asteroid observers.
The object's evident extrasolar origin motivated additional observations with more sensitive instruments including the Hubble Space Telescope.
'Oumuamua did not pass near enough to the Earth for a radar observation.

The Minor Planet Center collects those [observations here](https://minorplanetcenter.net/db_search/show_object?object_id=1I).
In the table of orbital elements, the 0.4 arcsecond residual is the root-mean-square difference between positions computed using those elements and positions actually observed.
In the observation table, the magnitude column indicates which [photometric filter](https://en.wikipedia.org/wiki/Photometric_system) was used, e.g. G or R for greenish or reddish bands of visible light.
Pan-STARRS filter w passes a wide band including most of the visible band and some near infrared ([Tonry et al. 2012](https://ui.adsabs.harvard.edu/abs/2012ApJ...750...99T/abstract) table 4).

[JPL's estimate](https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=1I) of 'Oumuamua's orbital elements uses the same observations and includes uncertainties.
They estimate about 1000 km error in perihelion distance (q), 23 seconds error in perihelion time (tp), and 1 arcsecond error in inclination (i) and ascending node longitude (node).
If you follow the Ephemeris link from there, and specify

Ephemeris Type: **VECTORS**
  
Table Settings: quantities code=**2x**

then HORIZONS gives Cartesian position and velocity uncertainties based on dynamical simulation.
These are larger now than when it was observed, and still larger a few months before discovery.

> **Comments:**
> **username_0**: OK. The answer is quite clear now.  

---

