# Tracking OSIRIS-REX

Where could I get real time telemetries for OSIRIS-REX? On official site I can only find "graphical simulated future telemetries", which are not very useful, also because each AAM is stated to occur exactly at midnight and I know it's not true:

I also found this site, but where does it pick data from?

https://programmi.000webhostapp.com/hayabusa2/simulator/simulator3.html

• there is no question about the simulator. The answer to the question about data will allow setting up the simulator. – jumpjack Oct 29 '18 at 16:07
• okay I understand. – uhoh Oct 29 '18 at 16:14
• My understanding is that whereisroadster.com gets its data from Horizons (see my answer) but it is less accurate there. See answers to Why does this site show Starman's position so far from what Horizons gives? for information by the site's developer. – uhoh Oct 30 '18 at 3:45

Where could I get real time telemetries for OSIRIS-REX?

For deep space missions, the spacecraft don't really "know" where they are and don't send position information back to Earth in telemetry as such.

Instead, people here interpret signals from the spacecraft (mostly round-trip time delays and doppler shifts) to get line-of-sight distance and speed. Over time this is compiled, and matched with a numerical orbit simulator based on gravity from all solar system objects, radiation pressure from the Sun, and other effects.

I believe the best that you can do is to look at the predicted future orbit in JPL's Horizons ephemeris. Right now the trajectory there is dated March 27, 2018, and the evens and maneuvers are specified to much finer detail than "midnight".

This will not reflect exactly where the spacecraft is, but it is likely that if the mission has deviated substantially from this plan, an updated ephemeris will be posted sooner or later.

For detailed directions with screenshots for how to download a table of positions and velocities (together known as state vectors) from Horizons, see this answer.

You may also want to review this answer to the question How to show spacecraft position, heading etc relative to an asteroid? which discusses relative vectors between OSIRIS-REx and the asteroid Bennu.

--

Currently the HORIZONS header for OSIRIS-REx state vectors includes:

Revised: Mar 27, 2018        OSIRIS-REx Spacecraft / (Sun)                 -64
http://www.asteroidmission.org
https://directory.eoportal.org/web/eoportal/satellite-missions/o/osiris-rex
http://www.nasa.gov/sites/default/files/atoms/files/osiris-rex_press_kit_0.pdf

NOTE:
2017-Sep-22 Earth gravity-assist flyby:
Closest-approach is nominally at 16:51:46 UTC, 23592 km from Earth center,
over 271.89346 deg. E, -74.80121 deg. (South). This is over Antarctica,
south of the tip of South America, about 420 km north of Vinson Massif,
the highest point in Antarctica.

BACKGROUND
OSIRIS-REx will explore 101955 Bennu (1999 RQ36), a carbonaceous B-type
asteroid whose regolith may provide insights on the early history of the
solar system.

MISSION EVENT SUMMARY (UTC)
2016  Sep 08 23:05 Launch from Cape Canaveral; daily 120 minutes windows from
Sep 8 - Oct 12. Atlas V w/Centaur upper stage.
2017  Sep 22 16:52 Earth flyby and gravity assist 23,592 km from geocenter
over {-74.80121 deg. S, 271.89346 deg. E}
2018  Aug          Bennu approach phase
Oct          Rendevous with asteroid
Nov          Estimate mass, shape, and spin state models
2019  Jan          Begin detailed mapping; identify candidate sample sites
May          Sorties to examine 4 candidate sample sistes
Sep          Collect sample > 60 grams
Oct          Quiescent operations in Bennu's heliocentric orbit
2021  Mar          Start return cruise and transport sample back to Earth
2023  Sep 24       Sample recovery on Earth

MISSION OBJECTIVES
* Map the asteroid
* Return and analyze a sample of Bennu's surface
* Document the sample site
* Measure the orbit deviation caused by small non-gravitational forces
* Compare observations made at the asteroid to ground-based observations

SPACECRAFT PHYSICAL DATA:
Length             : 20.25 ft (6.2 m) with solar panels deployed
Width             : 8 ft (2.4 m) x 8 ft (2.4 m)
Height             : 10.33 ft (3.2 m)
TAGSAM Length      : 11 ft (3.4 m) ("Touch-and-Go Camera System")
Dry mass (unfueled): 1,940 lbs (880 kg)
Wet mass (fueled)  : 4,650 lbs (2,110 kg)
Power              : Two solar panels 91 ft^2 (8.5 m^2) generate 1226 to
3000 watts, depending on distance from the Sun

SPACECRAFT TRAJECTORY
Post-launch spacecraft reference trajectory. Updated as warranted, as the
mission progresses. Corresponding Bennu trajectory is JPL #76, sb-101955-76.
[NOTE: To generate ephemerides of the destination asteroid (Bennu) (i.e.,
as a target), do a look-up using integer code "2101955" (NO semi-colon).
To use the asteroid as an observing point (i.e., produce ephemerides
relative to Bennu), set the coordinate center to "@2101955".]

Trajectory name                           Start (TDB)          Stop (TDB)
------------------------------------   -----------------   -----------------
orx_160909_171201_170830_od023_v1      2016-Sep-09 07:00   2017-May-01 00:01
orx_170501_180710_171005_od027_v1      2017-May-01 00:00   2017-Oct-06 00:01
orx_171006_231024_171005_refod027_v1   2017-Oct-06 00:01   2023-Oct-23 00:00

• thanks, I thought Horizons could only provide ephemeris for natural bodies, not spacecrafts! – jumpjack Oct 30 '18 at 9:22
• about relative position between a spacecraft and "its" asteroid, I read that after crossing the <200km distance threshold, JAXA switched from doppler method to "local" method (imaging and LIDAR) to figure out Hayabusa distance from Bennu, as precision of "remote methods" across hundreds of millions of km is around +/- 100 km, of course not acceptable if your around 100km far from a body! – jumpjack Oct 30 '18 at 9:24
• @jumpjack Oh, just updated a missing link to my answer above. Yes, Jaxa's visit to Ryugu (not Bennu) is very different because of the nature of that mission. See How could JAXA not know when Hayabusa2 will arrive at asteroid Ryugu? and also Nature of Hayabusa-2's “Home Position” relative to Ryugu? Is it Ruygu's L1? – uhoh Oct 30 '18 at 9:36

Found the solution thanks to uhoh.

Use this URL to request Osiris-Rex ephemeris from NASA Horizons site:

https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27ORX%27&MAKE_EPHEM=%27YES%27%20&TABLE_TYPE=%27OBSERVER%27&START_TIME=%272018-10-01%27&STOP_TIME=%272018-10-28%27&STEP_SIZE=%271%20d%27%20&QUANTITIES=%271,9,20,23,24%27&CSV_FORMAT=%27YES%27

Which corresponds to this batch command:

COMMAND='ORX'

MAKE_EPHEM='YES'

TABLE_TYPE='OBSERVER'

START_TIME='2018-10-01'

STOP_TIME='2018-10-28'

STEP_SIZE='1 d'

QUANTITIES='1,9,20,23,24'

CSV_FORMAT='YES'

Target body must be specified as a code: "ORX" is for "Osiris Rex", "1999%20RQ36" is for Bennu. It's the code within square brackets in line "Target Bod" in this page: https://ssd.jpl.nasa.gov/horizons.cgi

Data to be shown can also be set in that page; once finished setting up input parameters, click on "show batch-file data" link to display the commands as a list, then turn them into an URL: replace ' by %27 , replace spaces by %20 , replace carriage returns by "&".

This url provide ephemeris for Osiris-Rex (object "-64") in terms of 3d vectors for distance and speed in km and km/s w.r.t Earth :

https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%20%27-64%27&CENTER=%20%27500@0%27&MAKE_EPHEM=%20%27YES%27&TABLE_TYPE=%20%27VECTOR%27&START_TIME=%20%272018-10-1%27&STOP_TIME=%20%272018-10-30%27&STEP_SIZE=%20%271%20d%27&CAL_FORMAT=%20%27CAL%27&TIME_DIGITS=%20%27SECONDS%27&ANG_FORMAT=%20%27HMS%27&OUT_UNITS=%20%27KM-S%27&RANGE_UNITS=%20%27KM%27&APPARENT=%20%27AIRLESS%27&SUPPRESS_RANGE_RATE=%20%27NO%27&SKIP_DAYLT=%20%27NO%27&EXTRA_PREC=%20%27NO%27&R_T_S_ONLY=%20%27NO%27&REF_SYSTEM=%20%27J2000%27&CSV_FORMAT=%20%27NO%27&OBJ_DATA=%20%27YES%27&QUANTITIES=%20%2720,21,22,39,40%27&

This url provides same data for Bennu asteroid (object "1999 RQ36") :

https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%20%271999%20RQ36%27&CENTER=%20%27500@399%27&MAKE_EPHEM=%20%27YES%27&TABLE_TYPE=%20%27OBSERVER%27&START_TIME=%20%272018-10-1%27&STOP_TIME=%20%272018-10-30%27&STEP_SIZE=%20%271%20d%27&CAL_FORMAT=%20%27CAL%27&TIME_DIGITS=%20%27SECONDS%27&ANG_FORMAT=%20%27HMS%27&OUT_UNITS=%20%27KM-S%27&RANGE_UNITS=%20%27KM%27&APPARENT=%20%27AIRLESS%27&SUPPRESS_RANGE_RATE=%20%27NO%27&SKIP_DAYLT=%20%27NO%27&EXTRA_PREC=%20%27NO%27&R_T_S_ONLY=%20%27NO%27&REF_SYSTEM=%20%27J2000%27&CSV_FORMAT=%20%27NO%27&OBJ_DATA=%20%27YES%27&QUANTITIES=%20%2720,21,22,39,40%27&

• In this case I think it is better to accept this answer because it is the best answer to your question and provides exactly what you need. Doing so helps direct future readers to this solution. My answer contains background information and people will still see it. – uhoh Oct 30 '18 at 11:00
• I am not allowed to choose my answer as the best one till tomorrow, anyway I removed the check form yours. – jumpjack Oct 30 '18 at 12:39