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                                                                     EXHIBIT 5.1

                     [LETTERHEAD OF HOGAN & HARTSON L.L.P.]

                                  August 8, 2003

Board of Directors
XM Satellite Radio Inc.
1500 Eckington Place, N.E.
Washington, D.C. 20002

Ladies and Gentlemen:

          This firm has acted as counsel to XM Satellite Radio Inc., a Delaware
corporation (the "COMPANY"), and XM Satellite Radio Holdings Inc., a Delaware
corporation (the "GUARANTOR"), in connection with their Registration Statement
on Form S-4, as amended (the "REGISTRATION STATEMENT"), filed with the
Securities and Exchange Commission and relating to the proposed offering of up
to $185,000,000 in aggregate principal amount of 12% Senior Secured Notes due
2010 (the "EXCHANGE NOTES") guaranteed by the Guarantor (the "EXCHANGE
GUARANTEE") in exchange for up to $185,000,000 in aggregate principal amount of
the Company's outstanding 12% Senior Secured Notes due 2010 (the "OUTSTANDING
NOTES") guaranteed by the Guarantor (the "OUTSTANDING GUARANTEE"). This opinion
letter is furnished to you at your request to enable you to fulfill the
requirements of Item 601(b)(5) of Regulation S-K, 17 C.F.R. Section
229.601(b)(5), in connection with the Registration Statement.

          For purposes of this opinion letter, we have examined copies of the
following documents (the "DOCUMENTS"):

1.  An executed copy of the Registration Statement.

2.  An executed copy of the Indenture, dated June 17, 2003 (the "INDENTURE"), by
and between the Company, the Guarantor and The Bank of New York, including the
form of Exchange Note to be issued pursuant thereto.

3.  An executed copy of the Outstanding Guarantee, dated June 17, 2003.

4.  The form of the Exchange Guarantee, as such form is set forth in the
Indenture.

5.  The Restated Certificate of Incorporation of the Company, as amended, as
certified by the Secretary of State of the State of Delaware on July 18, 2003
and as certified by the Secretary of the Company on the date hereof as being
complete, accurate and in effect.

6.  The Restated Bylaws of the Company, as amended, as certified by the
Secretary of the Company on the date hereof as being complete, accurate and in
effect.

7.  Resolutions of the Board of Directors of the Company adopted at a meeting
held on June 3, 2003, minutes of a meeting of the Board of Directors held on
July 17, 2003 and resolutions of the Finance Committee of the Board of Directors
adopted at a meeting held on June 12, 2003, as certified by the Secretary of the
Company on the date hereof as being complete, accurate and in effect, relating
to the issuance and sale of the Exchange Notes, the preparation and filing of
the Registration Statement and arrangements in connection therewith.

8.  The Restated Certificate of Incorporation of the Guarantor, as amended, as
certified by the Secretary of State of the State of Delaware on July 18, 2003
and as certified by the Secretary of the Guarantor on the date hereof as being
complete, accurate and in effect.

9   The Restated Bylaws of the Guarantor, as amended, as certified by the
Secretary of the Guarantor on the date hereof as being complete, accurate and in
effect.

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10. Certain resolutions of the Board of Directors of the Guarantor adopted at a
meeting held on June 3, 2003, minutes of a meeting of the Board of Directors
held on July 17, 2003 and resolutions of the Finance Committee of the Board of
Directors adopted at a meeting held on June 12, 2003, as certified by the
Secretary of the Guarantor on the date hereof as being complete, accurate and in
effect, relating to, among other things, the issuance of the Exchange Guarantee
in connection with the exchange of the Exchange Notes for the Outstanding Notes
with the Outstanding Guarantee thereon and arrangements in connection therewith.

          In our examination of the Documents, we have assumed the genuineness
of all signatures, the legal capacity of all natural persons, the accuracy and
completeness of all of the Documents, the authenticity of all originals of the
Documents, and the conformity to authentic original documents of all of the
Documents submitted to us as copies (including telecopies). This opinion letter
is given, and all statements herein are made, in the context of the foregoing.

          This opinion letter is based as to matters of law solely on (i) the
Delaware General Corporation Law, as amended, and (ii) the laws of the State of
New York (but not including any statutes, ordinances, administrative decisions,
rules or regulations of any political subdivision of the State of New York). We
express no opinion herein as to any other laws, statutes, ordinances, rules or
regulations. As used herein, the terms "Delaware General Corporation Law, as
amended" and "the laws of the State of New York" include the statutory
provisions contained therein, all applicable provisions of the Delaware and New
York Constitutions and reported judicial decisions interpreting these laws. With
respect to clause (ii) above, the opinion expressed herein is based on a review
of those laws that, in our experience, are generally recognized as applicable to
the transactions contemplated in the Documents.

          Based upon, subject to and limited by the foregoing, we are of the
opinion that the Exchange Notes have been duly authorized on behalf of the
Company and the Exchange Guarantee has been duly authorized on behalf of the
Guarantor and that, (i) following the effectiveness of the Registration
Statement and receipt by the Company of the Outstanding Notes with the
Outstanding Guarantee thereon in exchange for the Exchange Notes with the
Exchange Guarantee thereon as specified in the resolutions of the Board of
Directors of the Company and the Guarantor referred to above, and (ii) assuming
due execution, authentication, issuance and delivery of the Exchange Notes and
the Exchange Guarantee as provided in the Indenture, the Exchange Notes will
constitute valid and binding obligations of the Company, and the Exchange
Guarantee will constitute a valid and binding obligation of the Guarantor.

          This opinion letter has been prepared for your use in connection with
the Registration Statement. We assume no obligation to advise you of any changes
in the foregoing subsequent to the effective date of the Registration Statement.

          In addition to the qualifications, exceptions and limitations
elsewhere set forth in this opinion letter, our opinions expressed above are
also subject to the effect of: (1) bankruptcy, insolvency, reorganization,
receivership, moratorium or other laws affecting creditors' rights (including,
without limitation, the effect of statutory and other law regarding fraudulent
conveyances, fraudulent transfers and preferential transfers); and (2) the
exercise of judicial discretion and the application of principles of equity
including, without limitation, requirements of good faith, fair dealing,
reasonableness, conscionability and materiality (regardless of whether the
applicable agreements are considered in a proceeding in equity or at law).

          We hereby consent to the filing of this opinion letter as Exhibit 5.1
to the Registration Statement and to the reference to this firm under the
caption "Legal Matters" in the prospectus constituting a part of the
Registration Statement. In giving this consent, we do not thereby admit that we
are an "expert" within the meaning of the Securities Act of 1933, as amended.


                                          Very truly yours,

                                          /s/ HOGAN & HARTSON L.L.P.

                                          HOGAN & HARTSON L.L.P.